Built transmission for boost, what is needed ?
06-24-2010, 06:25 PM
#21
Senior Member
SL Member
Join Date: Apr 2009
Location: Buffalo, NY
Posts: 782
Things that can fail in a transmission causing catastrophic failure.
1. Differentials: Differentials are tasked with taking the all the torque multiplied by the gear set and multiplying it again through a ring gear and then changing the direction of the power flow. Power flow is actually transferred through the carrier (case) of the differential and sent to whatever is connected to it. Things that can happen here include gears shredding internally depending on the design. Teeth can be damaged on the ring gear from improper contact pattern between the ring and pinion.
There are two basic types of Differentials. Open and Limited slip/locking. Open differentials have a spider gear setup accompanied by a center shaft to keep them in place. This center shaft is normally held in with a small bolt, roll pin or just pressed in place. Most OEM non-sports car types (tC) are open type differentials. When there is a lot of wheel hop, wheel spin or excessive amounts of torque applied causing sudden vibration or shocks to the differential the pins can come loose from their carrier sliding out causing the spiders to move out of orientation and the pin to contact the transmission case. If done at any sort of road speed it usually results in a hole or full on shredding of the transmission case. Which usually makes that transmission un-salvageable. Spiders normally get trashed in the process as well.
This is why it is important to have a strong differential that can with stand sudden shocks of power transfer. If you have good suspension and or slicks then the problem has just become worse because you have to overcome more friction (traction) to get going and thus increases the load on the differential.
Strong diffs available for the tC include the TRD/Quaife (TRD is a quaife) and the OS giken differential. Both are stronger than stock. Having driven both differentials I would recommend the OS Giken diff. It's pretty amazing how well it works. They both work well and the OS requires more frequent fluid changes being a clutch type diff but the feel is amazing.
2. Gears: Gears are always in constant mesh. They are always spinning. However we generally only concern ourselves with the ones we have selected to provide power to the road. We of course do this by shifting into a gear. This action locks a particular gear to the main shaft and makes it a driving gear, transferring power to a driven gear it is in constant contact with on the countershaft. Power is sent then through these shafts to the pinion gear which turns the ring gear on the differential we discussed earlier also known as the Final Drive assembly.
Things that can fail with gears. There are numerous factors that can contribute to gear failure, and most of these factors when added up in any certain order will almost always have the same end result. Sheared teeth from a gear. Gears are strong hardened steel (most times) and their physical dimensional sizes are calculated by engineers to be just large enough to handle the torque of the given (stock) application and be light enough to not sacrifice CAFE (corporate average fuel economy) ratings and small enough as to not spend too much money on making them.
Gears are doomed from the get go. So when more torque is applied to a gear it has to transfer that power with out failing. Let us use the tC as an example. The stock torque rating at the flywheel is 162 lb/ft of torque. The average turbocharged tC that is running 8psi of boost can range from 260-280 lb/ft of torque to the wheels! Now lets take the higher of the two numbers, and add 15% for drivetrain loss (this is power lost that is needed to move the weight of the parts inside the transmission and friction). We arrive at 322lb/ft of torque. That is a whopping 98% increase in torque we are now asking our gears to handle. Grudgingly, they abide.
Now the problem here is that as we move up the gear shift the drive gears begin to get smaller and the driven gears being to get larger. The ratios change and therefore rotational speeds change. The smaller the gear gets the faster it turns in relation to the gear it is driving. The faster it rotates the more friction it encounters. Friction = Heat generated. So we apply more power and generate more heat from a gear that was designed to handle 98% less power from the factory. Think about this for a moment.
Let us also take into consideration what torque is. It is a measurement of twisting force. Yes, twisting force. So when you accelerate everything in your power train is being twisted. The case that holds all of these gears in proper orientation to each other is no exception. When sudden torque is generated and applied through good traction the case of the transmission flexes/twists in the direction of engine rotation. You can sort of see this phenomena if you rev your engine and watch the entire engine rotate one direction or the other. The same is happening to everything that moves inside, you just can't see it. So when the case flexes the gear shafts that are suspended by bearings and races are pulled out of their desired positions and the gears that have always been in constant mesh begin to change their contact pattern. Generally they move outward and instead of driving the full tooth of the gear they begin to drive the outer portion of the tooth, the tip or heal of the tooth. When this happens all the torque that is generated is now applied to a reduced section of the gear tooth. Now, if our gears are having trouble keeping up with the torque that we are making now, just think of what happens then. Additional force and heat build up over time will cause micro cracks to form in the gear teeth, minor chips may occur as well, but overall complete failure of that gear is imminent.
Things that lead up to this, well torque for one. Lack of lubrication or the wrong type of lubrication. Lack of lubrication will not allow the gears to be properly splash lubed and thus cooled. Slicks don't help the situation but are a necessary evil if we want to go fast. In the search of speed we normally forget about the intended design of the parts we use in place of the intended use. Meaning these parts were designed for a cheap passenger car but we use them for a cheap race car. That's fine! We as users must understand the consequences of our actions and it helps to swallow those when we understand how the parts work and why they fail.
Things that can protect this.....well there isn't a whole lot since it's mostly a factor of physical size. Things you can do include gear detailing, which should be done by a professional experienced in this kind of work, Cryo treating as this realigns the molecular structure of the material to make it much more uniform and thus stronger. REM treatment, this is a polishing process used to stress relieve the gears and created a better surface finish for oil shedding and better lubrication. There is the possibility of creating a replacement straight cut gear set with dog tooth engagement but that is very very expensive and is probably necessary for those drag racing or road racing on a consistent basis. Ptuning could have benefited from a Dog Box during their last race season based on the problems they were having with their transmission. Straight cut gears are noisy but stronger than helical cut gears. A dog tooth engagement relies on far fewer teeth on a dog ring and not a synchro ring to engage the next gear. It is sloppy and mechanical but always works without fail. It's rough, but I love it! Slam it into gear and go!
3. Synchronizers: Synchros aid in gear change, they are not necessary and for many many years transmissions were manufactured without them. The term double clutching was generated because of this. It was what you had to do to properly shift a transmission back in the day. Synchros help match the speeds of the gear chosen to engage the main shaft. Because of the nature of gear ratios and all the factors that go into propelling a car things are happening inside the transmission at different rates of speed. In order to make a smooth transition from one gear to another we must either slow down or speed up (depending on up shifting or down shifting) the chosen gear we are going to go in. Synchros are made from brass almost exclusively some have friction liners some dont. These are wear items believe it or not. Just like your clutch, someday they will die. Depending on the amount of lubrication they see and how poor of a driver you are will determine their life. Clutches that are improperly adjusted will not fully disengage when the pedal is pressed allowing power to be continuously transferred to the input/mainshaft of the transmission making the synchros job very very difficult. It is fighting forces on both sides of the shaft and the result is either a "grind" or a blocked shift. Everyone on here has felt that at one time or another. And on that note, you don't grind gears, you grind synchros.
Things that cause these to fail include lack of lubrication, improper shift timing, mis-adjusted clutches and misadjusted clutch cables (if there is an adjustement), broken or bent shift forks will also cause this but kind of rare on the tC.
There are a few other potential failures in the tC transmission that are common to most all transmissions and to go into them all is way more than I have already typed. Just know that most are caused by lack of transmission fluid or dirty transmission fluid. So keep and eye on the level and change it on a regular basis.
1. Differentials: Differentials are tasked with taking the all the torque multiplied by the gear set and multiplying it again through a ring gear and then changing the direction of the power flow. Power flow is actually transferred through the carrier (case) of the differential and sent to whatever is connected to it. Things that can happen here include gears shredding internally depending on the design. Teeth can be damaged on the ring gear from improper contact pattern between the ring and pinion.
There are two basic types of Differentials. Open and Limited slip/locking. Open differentials have a spider gear setup accompanied by a center shaft to keep them in place. This center shaft is normally held in with a small bolt, roll pin or just pressed in place. Most OEM non-sports car types (tC) are open type differentials. When there is a lot of wheel hop, wheel spin or excessive amounts of torque applied causing sudden vibration or shocks to the differential the pins can come loose from their carrier sliding out causing the spiders to move out of orientation and the pin to contact the transmission case. If done at any sort of road speed it usually results in a hole or full on shredding of the transmission case. Which usually makes that transmission un-salvageable. Spiders normally get trashed in the process as well.
This is why it is important to have a strong differential that can with stand sudden shocks of power transfer. If you have good suspension and or slicks then the problem has just become worse because you have to overcome more friction (traction) to get going and thus increases the load on the differential.
Strong diffs available for the tC include the TRD/Quaife (TRD is a quaife) and the OS giken differential. Both are stronger than stock. Having driven both differentials I would recommend the OS Giken diff. It's pretty amazing how well it works. They both work well and the OS requires more frequent fluid changes being a clutch type diff but the feel is amazing.
2. Gears: Gears are always in constant mesh. They are always spinning. However we generally only concern ourselves with the ones we have selected to provide power to the road. We of course do this by shifting into a gear. This action locks a particular gear to the main shaft and makes it a driving gear, transferring power to a driven gear it is in constant contact with on the countershaft. Power is sent then through these shafts to the pinion gear which turns the ring gear on the differential we discussed earlier also known as the Final Drive assembly.
Things that can fail with gears. There are numerous factors that can contribute to gear failure, and most of these factors when added up in any certain order will almost always have the same end result. Sheared teeth from a gear. Gears are strong hardened steel (most times) and their physical dimensional sizes are calculated by engineers to be just large enough to handle the torque of the given (stock) application and be light enough to not sacrifice CAFE (corporate average fuel economy) ratings and small enough as to not spend too much money on making them.
Gears are doomed from the get go. So when more torque is applied to a gear it has to transfer that power with out failing. Let us use the tC as an example. The stock torque rating at the flywheel is 162 lb/ft of torque. The average turbocharged tC that is running 8psi of boost can range from 260-280 lb/ft of torque to the wheels! Now lets take the higher of the two numbers, and add 15% for drivetrain loss (this is power lost that is needed to move the weight of the parts inside the transmission and friction). We arrive at 322lb/ft of torque. That is a whopping 98% increase in torque we are now asking our gears to handle. Grudgingly, they abide.
Now the problem here is that as we move up the gear shift the drive gears begin to get smaller and the driven gears being to get larger. The ratios change and therefore rotational speeds change. The smaller the gear gets the faster it turns in relation to the gear it is driving. The faster it rotates the more friction it encounters. Friction = Heat generated. So we apply more power and generate more heat from a gear that was designed to handle 98% less power from the factory. Think about this for a moment.
Let us also take into consideration what torque is. It is a measurement of twisting force. Yes, twisting force. So when you accelerate everything in your power train is being twisted. The case that holds all of these gears in proper orientation to each other is no exception. When sudden torque is generated and applied through good traction the case of the transmission flexes/twists in the direction of engine rotation. You can sort of see this phenomena if you rev your engine and watch the entire engine rotate one direction or the other. The same is happening to everything that moves inside, you just can't see it. So when the case flexes the gear shafts that are suspended by bearings and races are pulled out of their desired positions and the gears that have always been in constant mesh begin to change their contact pattern. Generally they move outward and instead of driving the full tooth of the gear they begin to drive the outer portion of the tooth, the tip or heal of the tooth. When this happens all the torque that is generated is now applied to a reduced section of the gear tooth. Now, if our gears are having trouble keeping up with the torque that we are making now, just think of what happens then. Additional force and heat build up over time will cause micro cracks to form in the gear teeth, minor chips may occur as well, but overall complete failure of that gear is imminent.
Things that lead up to this, well torque for one. Lack of lubrication or the wrong type of lubrication. Lack of lubrication will not allow the gears to be properly splash lubed and thus cooled. Slicks don't help the situation but are a necessary evil if we want to go fast. In the search of speed we normally forget about the intended design of the parts we use in place of the intended use. Meaning these parts were designed for a cheap passenger car but we use them for a cheap race car. That's fine! We as users must understand the consequences of our actions and it helps to swallow those when we understand how the parts work and why they fail.
Things that can protect this.....well there isn't a whole lot since it's mostly a factor of physical size. Things you can do include gear detailing, which should be done by a professional experienced in this kind of work, Cryo treating as this realigns the molecular structure of the material to make it much more uniform and thus stronger. REM treatment, this is a polishing process used to stress relieve the gears and created a better surface finish for oil shedding and better lubrication. There is the possibility of creating a replacement straight cut gear set with dog tooth engagement but that is very very expensive and is probably necessary for those drag racing or road racing on a consistent basis. Ptuning could have benefited from a Dog Box during their last race season based on the problems they were having with their transmission. Straight cut gears are noisy but stronger than helical cut gears. A dog tooth engagement relies on far fewer teeth on a dog ring and not a synchro ring to engage the next gear. It is sloppy and mechanical but always works without fail. It's rough, but I love it! Slam it into gear and go!
3. Synchronizers: Synchros aid in gear change, they are not necessary and for many many years transmissions were manufactured without them. The term double clutching was generated because of this. It was what you had to do to properly shift a transmission back in the day. Synchros help match the speeds of the gear chosen to engage the main shaft. Because of the nature of gear ratios and all the factors that go into propelling a car things are happening inside the transmission at different rates of speed. In order to make a smooth transition from one gear to another we must either slow down or speed up (depending on up shifting or down shifting) the chosen gear we are going to go in. Synchros are made from brass almost exclusively some have friction liners some dont. These are wear items believe it or not. Just like your clutch, someday they will die. Depending on the amount of lubrication they see and how poor of a driver you are will determine their life. Clutches that are improperly adjusted will not fully disengage when the pedal is pressed allowing power to be continuously transferred to the input/mainshaft of the transmission making the synchros job very very difficult. It is fighting forces on both sides of the shaft and the result is either a "grind" or a blocked shift. Everyone on here has felt that at one time or another. And on that note, you don't grind gears, you grind synchros.
Things that cause these to fail include lack of lubrication, improper shift timing, mis-adjusted clutches and misadjusted clutch cables (if there is an adjustement), broken or bent shift forks will also cause this but kind of rare on the tC.
There are a few other potential failures in the tC transmission that are common to most all transmissions and to go into them all is way more than I have already typed. Just know that most are caused by lack of transmission fluid or dirty transmission fluid. So keep and eye on the level and change it on a regular basis.
06-24-2010, 06:47 PM
#22
Senior Member
Music City Scions
Scikotics
SL Member
Join Date: Jun 2005
Location: TN
Posts: 16,747
You say that our trannys don't "blow up", but how do you know that? My carrier bearing and the wrist pin in the diff went out, milling a hole in the case, sending fluid everywhere, starving the other gears for fluid untill it wouldn't even turn over. This all happened in about 20 seconds. I'd say it blew up.
The problem I have with our tranny is that there is no aftermarket support and if you make any appreciable about of power, you can't really put it down without fear of losing 4th.
The problem I have with our tranny is that there is no aftermarket support and if you make any appreciable about of power, you can't really put it down without fear of losing 4th.
No hard feelings. I'm going by prior data supplied to us from the Scions that abuse this stuff season to season.
- Rado ran the stock transmission at 700-800whp levels during Time Attack for quite some time.
- PTuning ran the stock transmission at 330-550whp levels for two seasons, and until recently REM treated the gears. However, I think they still blew 4th gear out after the REM treatment (4th gear is to me the only thing I would consider flimsy in our trannies). This was at about 550+whp on PTuning's dyno.
- When you say flimsy compared to other cars, I don't think you have done enough research into other cars to know how well our trans stacks up to theirs. My old DE 350z for example (2003 model). Trans is good for about 400whp and then you start having all kinds of problems. Heck, I had problems at near stock power levels. S2000 transmission I understand isn't that much better either, that and the rear end is prone to failure. I'm a member over on an XRS forum. They literally GRENADE their transmissions with stock power if they go to the drag strip and launch the car to many times.
All in all, I'm pretty proud of our trans. Only problems I have encountered is a 5th gear synchro going out back on a street race I did with a friend of mine. That's a pretty rare thing, cause I don't know anyone else who screwed up 5th gear. So, for that to be my only tranny problem, with the amount of abuse my tC see's on a regular basis, I have to tip my hat to it.
Drivetrain wise, my biggest hassle is blowing clutches.
Last edited by rhythmnsmoke; 06-24-2010 at 06:57 PM.
06-24-2010, 06:56 PM
#23
Senior Member
Music City Scions
Scikotics
SL Member
Join Date: Jun 2005
Location: TN
Posts: 16,747
The driver side axle ticks me off too...forgot to add that in. If I could afford Straight Cut gears I would have them already though, just putting that out there.
Car is WICKED with Straight Cut gear box. Strictly race application though.
PS...I run the TRD/Quaife LSD in my tC.
Car is WICKED with Straight Cut gear box. Strictly race application though.
PS...I run the TRD/Quaife LSD in my tC.
06-24-2010, 08:01 PM
#24
No hard feelings. I'm going by prior data supplied to us from the Scions that abuse this stuff season to season.
- Rado ran the stock transmission at 700-800whp levels during Time Attack for quite some time.
- PTuning ran the stock transmission at 330-550whp levels for two seasons, and until recently REM treated the gears. However, I think they still blew 4th gear out after the REM treatment (4th gear is to me the only thing I would consider flimsy in our trannies). This was at about 550+whp on PTuning's dyno.
- When you say flimsy compared to other cars, I don't think you have done enough research into other cars to know how well our trans stacks up to theirs. My old DE 350z for example (2003 model). Trans is good for about 400whp and then you start having all kinds of problems. Heck, I had problems at near stock power levels. S2000 transmission I understand isn't that much better either, that and the rear end is prone to failure. I'm a member over on an XRS forum. They literally GRENADE their transmissions with stock power if they go to the drag strip and launch the car to many times.
All in all, I'm pretty proud of our trans. Only problems I have encountered is a 5th gear synchro going out back on a street race I did with a friend of mine. That's a pretty rare thing, cause I don't know anyone else who screwed up 5th gear. So, for that to be my only tranny problem, with the amount of abuse my tC see's on a regular basis, I have to tip my hat to it.
Drivetrain wise, my biggest hassle is blowing clutches.
- Rado ran the stock transmission at 700-800whp levels during Time Attack for quite some time.
- PTuning ran the stock transmission at 330-550whp levels for two seasons, and until recently REM treated the gears. However, I think they still blew 4th gear out after the REM treatment (4th gear is to me the only thing I would consider flimsy in our trannies). This was at about 550+whp on PTuning's dyno.
- When you say flimsy compared to other cars, I don't think you have done enough research into other cars to know how well our trans stacks up to theirs. My old DE 350z for example (2003 model). Trans is good for about 400whp and then you start having all kinds of problems. Heck, I had problems at near stock power levels. S2000 transmission I understand isn't that much better either, that and the rear end is prone to failure. I'm a member over on an XRS forum. They literally GRENADE their transmissions with stock power if they go to the drag strip and launch the car to many times.
All in all, I'm pretty proud of our trans. Only problems I have encountered is a 5th gear synchro going out back on a street race I did with a friend of mine. That's a pretty rare thing, cause I don't know anyone else who screwed up 5th gear. So, for that to be my only tranny problem, with the amount of abuse my tC see's on a regular basis, I have to tip my hat to it.
Drivetrain wise, my biggest hassle is blowing clutches.
06-24-2010, 09:51 PM
#26
Senior Member
SL Member
Join Date: Apr 2008
Location: Orlando, FL
Posts: 4,156
Things that can fail in a transmission causing catastrophic failure.
1. Differentials: Differentials are tasked with taking the all the torque multiplied by the gear set and multiplying it again through a ring gear and then changing the direction of the power flow. Power flow is actually transferred through the carrier (case) of the differential and sent to whatever is connected to it. Things that can happen here include gears shredding internally depending on the design. Teeth can be damaged on the ring gear from improper contact pattern between the ring and pinion.
There are two basic types of Differentials. Open and Limited slip/locking. Open differentials have a spider gear setup accompanied by a center shaft to keep them in place. This center shaft is normally held in with a small bolt, roll pin or just pressed in place. Most OEM non-sports car types (tC) are open type differentials. When there is a lot of wheel hop, wheel spin or excessive amounts of torque applied causing sudden vibration or shocks to the differential the pins can come loose from their carrier sliding out causing the spiders to move out of orientation and the pin to contact the transmission case. If done at any sort of road speed it usually results in a hole or full on shredding of the transmission case. Which usually makes that transmission un-salvageable. Spiders normally get trashed in the process as well.
This is why it is important to have a strong differential that can with stand sudden shocks of power transfer. If you have good suspension and or slicks then the problem has just become worse because you have to overcome more friction (traction) to get going and thus increases the load on the differential.
Strong diffs available for the tC include the TRD/Quaife (TRD is a quaife) and the OS giken differential. Both are stronger than stock. Having driven both differentials I would recommend the OS Giken diff. It's pretty amazing how well it works. They both work well and the OS requires more frequent fluid changes being a clutch type diff but the feel is amazing.
2. Gears: Gears are always in constant mesh. They are always spinning. However we generally only concern ourselves with the ones we have selected to provide power to the road. We of course do this by shifting into a gear. This action locks a particular gear to the main shaft and makes it a driving gear, transferring power to a driven gear it is in constant contact with on the countershaft. Power is sent then through these shafts to the pinion gear which turns the ring gear on the differential we discussed earlier also known as the Final Drive assembly.
Things that can fail with gears. There are numerous factors that can contribute to gear failure, and most of these factors when added up in any certain order will almost always have the same end result. Sheared teeth from a gear. Gears are strong hardened steel (most times) and their physical dimensional sizes are calculated by engineers to be just large enough to handle the torque of the given (stock) application and be light enough to not sacrifice CAFE (corporate average fuel economy) ratings and small enough as to not spend too much money on making them.
Gears are doomed from the get go. So when more torque is applied to a gear it has to transfer that power with out failing. Let us use the tC as an example. The stock torque rating at the flywheel is 162 lb/ft of torque. The average turbocharged tC that is running 8psi of boost can range from 260-280 lb/ft of torque to the wheels! Now lets take the higher of the two numbers, and add 15% for drivetrain loss (this is power lost that is needed to move the weight of the parts inside the transmission and friction). We arrive at 322lb/ft of torque. That is a whopping 98% increase in torque we are now asking our gears to handle. Grudgingly, they abide.
Now the problem here is that as we move up the gear shift the drive gears begin to get smaller and the driven gears being to get larger. The ratios change and therefore rotational speeds change. The smaller the gear gets the faster it turns in relation to the gear it is driving. The faster it rotates the more friction it encounters. Friction = Heat generated. So we apply more power and generate more heat from a gear that was designed to handle 98% less power from the factory. Think about this for a moment.
Let us also take into consideration what torque is. It is a measurement of twisting force. Yes, twisting force. So when you accelerate everything in your power train is being twisted. The case that holds all of these gears in proper orientation to each other is no exception. When sudden torque is generated and applied through good traction the case of the transmission flexes/twists in the direction of engine rotation. You can sort of see this phenomena if you rev your engine and watch the entire engine rotate one direction or the other. The same is happening to everything that moves inside, you just can't see it. So when the case flexes the gear shafts that are suspended by bearings and races are pulled out of their desired positions and the gears that have always been in constant mesh begin to change their contact pattern. Generally they move outward and instead of driving the full tooth of the gear they begin to drive the outer portion of the tooth, the tip or heal of the tooth. When this happens all the torque that is generated is now applied to a reduced section of the gear tooth. Now, if our gears are having trouble keeping up with the torque that we are making now, just think of what happens then. Additional force and heat build up over time will cause micro cracks to form in the gear teeth, minor chips may occur as well, but overall complete failure of that gear is imminent.
Things that lead up to this, well torque for one. Lack of lubrication or the wrong type of lubrication. Lack of lubrication will not allow the gears to be properly splash lubed and thus cooled. Slicks don't help the situation but are a necessary evil if we want to go fast. In the search of speed we normally forget about the intended design of the parts we use in place of the intended use. Meaning these parts were designed for a cheap passenger car but we use them for a cheap race car. That's fine! We as users must understand the consequences of our actions and it helps to swallow those when we understand how the parts work and why they fail.
Things that can protect this.....well there isn't a whole lot since it's mostly a factor of physical size. Things you can do include gear detailing, which should be done by a professional experienced in this kind of work, Cryo treating as this realigns the molecular structure of the material to make it much more uniform and thus stronger. REM treatment, this is a polishing process used to stress relieve the gears and created a better surface finish for oil shedding and better lubrication. There is the possibility of creating a replacement straight cut gear set with dog tooth engagement but that is very very expensive and is probably necessary for those drag racing or road racing on a consistent basis. Ptuning could have benefited from a Dog Box during their last race season based on the problems they were having with their transmission. Straight cut gears are noisy but stronger than helical cut gears. A dog tooth engagement relies on far fewer teeth on a dog ring and not a synchro ring to engage the next gear. It is sloppy and mechanical but always works without fail. It's rough, but I love it! Slam it into gear and go!
3. Synchronizers: Synchros aid in gear change, they are not necessary and for many many years transmissions were manufactured without them. The term double clutching was generated because of this. It was what you had to do to properly shift a transmission back in the day. Synchros help match the speeds of the gear chosen to engage the main shaft. Because of the nature of gear ratios and all the factors that go into propelling a car things are happening inside the transmission at different rates of speed. In order to make a smooth transition from one gear to another we must either slow down or speed up (depending on up shifting or down shifting) the chosen gear we are going to go in. Synchros are made from brass almost exclusively some have friction liners some dont. These are wear items believe it or not. Just like your clutch, someday they will die. Depending on the amount of lubrication they see and how poor of a driver you are will determine their life. Clutches that are improperly adjusted will not fully disengage when the pedal is pressed allowing power to be continuously transferred to the input/mainshaft of the transmission making the synchros job very very difficult. It is fighting forces on both sides of the shaft and the result is either a "grind" or a blocked shift. Everyone on here has felt that at one time or another. And on that note, you don't grind gears, you grind synchros.
Things that cause these to fail include lack of lubrication, improper shift timing, mis-adjusted clutches and misadjusted clutch cables (if there is an adjustement), broken or bent shift forks will also cause this but kind of rare on the tC.
There are a few other potential failures in the tC transmission that are common to most all transmissions and to go into them all is way more than I have already typed. Just know that most are caused by lack of transmission fluid or dirty transmission fluid. So keep and eye on the level and change it on a regular basis.
1. Differentials: Differentials are tasked with taking the all the torque multiplied by the gear set and multiplying it again through a ring gear and then changing the direction of the power flow. Power flow is actually transferred through the carrier (case) of the differential and sent to whatever is connected to it. Things that can happen here include gears shredding internally depending on the design. Teeth can be damaged on the ring gear from improper contact pattern between the ring and pinion.
There are two basic types of Differentials. Open and Limited slip/locking. Open differentials have a spider gear setup accompanied by a center shaft to keep them in place. This center shaft is normally held in with a small bolt, roll pin or just pressed in place. Most OEM non-sports car types (tC) are open type differentials. When there is a lot of wheel hop, wheel spin or excessive amounts of torque applied causing sudden vibration or shocks to the differential the pins can come loose from their carrier sliding out causing the spiders to move out of orientation and the pin to contact the transmission case. If done at any sort of road speed it usually results in a hole or full on shredding of the transmission case. Which usually makes that transmission un-salvageable. Spiders normally get trashed in the process as well.
This is why it is important to have a strong differential that can with stand sudden shocks of power transfer. If you have good suspension and or slicks then the problem has just become worse because you have to overcome more friction (traction) to get going and thus increases the load on the differential.
Strong diffs available for the tC include the TRD/Quaife (TRD is a quaife) and the OS giken differential. Both are stronger than stock. Having driven both differentials I would recommend the OS Giken diff. It's pretty amazing how well it works. They both work well and the OS requires more frequent fluid changes being a clutch type diff but the feel is amazing.
2. Gears: Gears are always in constant mesh. They are always spinning. However we generally only concern ourselves with the ones we have selected to provide power to the road. We of course do this by shifting into a gear. This action locks a particular gear to the main shaft and makes it a driving gear, transferring power to a driven gear it is in constant contact with on the countershaft. Power is sent then through these shafts to the pinion gear which turns the ring gear on the differential we discussed earlier also known as the Final Drive assembly.
Things that can fail with gears. There are numerous factors that can contribute to gear failure, and most of these factors when added up in any certain order will almost always have the same end result. Sheared teeth from a gear. Gears are strong hardened steel (most times) and their physical dimensional sizes are calculated by engineers to be just large enough to handle the torque of the given (stock) application and be light enough to not sacrifice CAFE (corporate average fuel economy) ratings and small enough as to not spend too much money on making them.
Gears are doomed from the get go. So when more torque is applied to a gear it has to transfer that power with out failing. Let us use the tC as an example. The stock torque rating at the flywheel is 162 lb/ft of torque. The average turbocharged tC that is running 8psi of boost can range from 260-280 lb/ft of torque to the wheels! Now lets take the higher of the two numbers, and add 15% for drivetrain loss (this is power lost that is needed to move the weight of the parts inside the transmission and friction). We arrive at 322lb/ft of torque. That is a whopping 98% increase in torque we are now asking our gears to handle. Grudgingly, they abide.
Now the problem here is that as we move up the gear shift the drive gears begin to get smaller and the driven gears being to get larger. The ratios change and therefore rotational speeds change. The smaller the gear gets the faster it turns in relation to the gear it is driving. The faster it rotates the more friction it encounters. Friction = Heat generated. So we apply more power and generate more heat from a gear that was designed to handle 98% less power from the factory. Think about this for a moment.
Let us also take into consideration what torque is. It is a measurement of twisting force. Yes, twisting force. So when you accelerate everything in your power train is being twisted. The case that holds all of these gears in proper orientation to each other is no exception. When sudden torque is generated and applied through good traction the case of the transmission flexes/twists in the direction of engine rotation. You can sort of see this phenomena if you rev your engine and watch the entire engine rotate one direction or the other. The same is happening to everything that moves inside, you just can't see it. So when the case flexes the gear shafts that are suspended by bearings and races are pulled out of their desired positions and the gears that have always been in constant mesh begin to change their contact pattern. Generally they move outward and instead of driving the full tooth of the gear they begin to drive the outer portion of the tooth, the tip or heal of the tooth. When this happens all the torque that is generated is now applied to a reduced section of the gear tooth. Now, if our gears are having trouble keeping up with the torque that we are making now, just think of what happens then. Additional force and heat build up over time will cause micro cracks to form in the gear teeth, minor chips may occur as well, but overall complete failure of that gear is imminent.
Things that lead up to this, well torque for one. Lack of lubrication or the wrong type of lubrication. Lack of lubrication will not allow the gears to be properly splash lubed and thus cooled. Slicks don't help the situation but are a necessary evil if we want to go fast. In the search of speed we normally forget about the intended design of the parts we use in place of the intended use. Meaning these parts were designed for a cheap passenger car but we use them for a cheap race car. That's fine! We as users must understand the consequences of our actions and it helps to swallow those when we understand how the parts work and why they fail.
Things that can protect this.....well there isn't a whole lot since it's mostly a factor of physical size. Things you can do include gear detailing, which should be done by a professional experienced in this kind of work, Cryo treating as this realigns the molecular structure of the material to make it much more uniform and thus stronger. REM treatment, this is a polishing process used to stress relieve the gears and created a better surface finish for oil shedding and better lubrication. There is the possibility of creating a replacement straight cut gear set with dog tooth engagement but that is very very expensive and is probably necessary for those drag racing or road racing on a consistent basis. Ptuning could have benefited from a Dog Box during their last race season based on the problems they were having with their transmission. Straight cut gears are noisy but stronger than helical cut gears. A dog tooth engagement relies on far fewer teeth on a dog ring and not a synchro ring to engage the next gear. It is sloppy and mechanical but always works without fail. It's rough, but I love it! Slam it into gear and go!
3. Synchronizers: Synchros aid in gear change, they are not necessary and for many many years transmissions were manufactured without them. The term double clutching was generated because of this. It was what you had to do to properly shift a transmission back in the day. Synchros help match the speeds of the gear chosen to engage the main shaft. Because of the nature of gear ratios and all the factors that go into propelling a car things are happening inside the transmission at different rates of speed. In order to make a smooth transition from one gear to another we must either slow down or speed up (depending on up shifting or down shifting) the chosen gear we are going to go in. Synchros are made from brass almost exclusively some have friction liners some dont. These are wear items believe it or not. Just like your clutch, someday they will die. Depending on the amount of lubrication they see and how poor of a driver you are will determine their life. Clutches that are improperly adjusted will not fully disengage when the pedal is pressed allowing power to be continuously transferred to the input/mainshaft of the transmission making the synchros job very very difficult. It is fighting forces on both sides of the shaft and the result is either a "grind" or a blocked shift. Everyone on here has felt that at one time or another. And on that note, you don't grind gears, you grind synchros.
Things that cause these to fail include lack of lubrication, improper shift timing, mis-adjusted clutches and misadjusted clutch cables (if there is an adjustement), broken or bent shift forks will also cause this but kind of rare on the tC.
There are a few other potential failures in the tC transmission that are common to most all transmissions and to go into them all is way more than I have already typed. Just know that most are caused by lack of transmission fluid or dirty transmission fluid. So keep and eye on the level and change it on a regular basis.
Holy WIN write up!
Im still on my OEM trans and OEM Axels Oem DIFF..
Preloading before launchs. And motul fluids have kept me in the green = )
06-26-2010, 05:23 PM
#33
Could we possibly make a "building your tranny for boost/making your tranny last under boost" sticky?? I can tell you I have been wanting to know some of this stuff for a looong time lol. I'm sure someone could definitely use this info before they go and really get on their turbo tc for the first time
10-06-2010, 06:32 PM
#35
Senior Member
SL Member
Join Date: Apr 2009
Location: Buffalo, NY
Posts: 782
I did not know this. This would be a great swap for guys that want higher trap speeds making double the torque
PPG would make some but get ready to spend out the ___.
PPG would make some but get ready to spend out the ___.
10-06-2010, 08:36 PM
#36
Senior Member
SL Member
Join Date: Dec 2005
Location: Miami, FL
Posts: 564
Cryo is cheap but who the hell knows if it even works. I would like to change the gears because cruzin sux in the TC. I heard you can you a Matrix tranny that has 6 gears anyone ever heard of this.
10-06-2010, 09:07 PM
#37
yea, and then they sold some, one of which i bought, and running with no issues. idk if they did anything other than adding LSD (as far as i know, they didnt)... all i know is the trans is in perfect condition and a note on the side of the trans said.... broke 3 axles. good trans.
10-06-2010, 10:00 PM
#39
Senior Member
SL Member
Join Date: Nov 2005
Location: WORLD WIDE Flossin
Posts: 13,376
if you want your gears to last: good fluid, propper driving, cryo treatment, and a upgrade your gears with others gears from the XRS trans. you can also order str8 cuts but my god that would be rape on the wallet and daily driving would suck.
it is rumored the new tc's 6sp bell housing just needs a new bracket and it works as a direct swap but i cannot confirm that yet
