elwaylite

iTrader: (1)

Mine seems to do it only in a slight decline, and I can imitate the same action manually. If I just hold the gas, then take my foot off completely, then tap it again, then let off. The rpm's bounce back and forth, back and forth.

Grease Monkey

I've noticed the same thing.... but only has happened 3-4 times in 4k miles. Right around 35mph it will sometimes drop to about 800rpm and go up to 1500rpm. I have a feeling it doesn't know what gear to be in.... Didn't see any TSB's last time I looked. My old VW used to do the same thing around 35-40.... Stoopid autos..... I'm just too lazy to drive a stick!

elwaylite

iTrader: (1)

Yeah, that may be. I notice mine, if it does it a few times, it finally downshift.

91cavgt

Well, if yours get worse, you can take it to where I took mine since we are both in the D/FW area. I went to Toyota of Lewisville. Yeah, it is a bit of a drive for you, but it helps when a dealership has seen a problem on another car, and they gave me a free loaner car while all of this is going on. Granted, it's just a Corolla, but hey, I didn't have to fork out rental money for it.

elwaylite

iTrader: (1)

Only problem with this issue is, even if it is an issue, its a hard one to duplicate. Im at 22k miles now, just have to monitor.

Grease Monkey

I'll just have to fix it myself...
<--- Toyota Tech

91cavgt

Mine is VERY easy to duplicate, however I had noticed it occasionally doing it a year ago (at around 18k miles). Used to, I could barely get it to do it on one road and you had to hold your tongue just right. Now though, all you need to do is find a flat road, hit cruise control at 35 mph, and it does it like crazy and it's non stop as long as the road is flat.


Maybe this is something that is gonna be more common as the later model Xb's get up there in miles?

elwaylite

iTrader: (1)

Thats what Im wondering, does it get worse with more mileage.

91cavgt

I'm gonna try to find out everything I can when I pick the car up so I can pass the info on to you guys.

91cavgt

Mine most definately did.

91cavgt

Yet another update!


The dealership called me today to tell me that I can pick up the car today, but the problem hasn't been fixed yet. That's right, they replaced the transmission and it did not fix the problem!!

My service advisor told me that Toyota Corporate is aware of the problem and they are trying to come up with a solution for it. Once a solution has been made then they will contact me and I will bring the car back in to get repaired.


On the way home I discovered something. I once thought that this problem only occured at around 35 mph. However, after hearing you guys explain very similar experiences at different speeds I decided to try cruise control at several different speeds. Here are the results;

30 mph - could not duplicate and did not act up
35 mph - acted up as usual and can duplicate
40 mph - acted up and can duplicate but only going down slight hills
45 mph - acted up and can duplicate but only going down moderate hills
50 mph - I think I got it to do it once


I am thinking more and more that this problem only occurs under VERY minimal throttle opening. At higher speeds it won't occur due to the throttle plate being more open and at lower speeds it won't happen because there is just not enough of a load on the motor.

So maybe this is a throttle problem and not a transmission problem? Maybe a dirty throttle body could be causing this? What do you guys think?

Grease Monkey

I bet monies that this is a ecu mapping issue....

When the 05-06 Avalon came out with the 6-speed auto some would have a 3-4 shift flare when cold... Toyota initially had us replace the transmission. Didn't fix squat. Then they had us replace the transmission valve body.... didn't work either. The geeks finally came out with a new flash for the ecu... and guess what.... it worked!!! It was a software issue all along...

Keep those updates coming!

elwaylite

iTrader: (1)

Thats what Im thinking. Software/throttle issue. His 40 and 45 mph comments are just what I see. I can then drive thru the same area with cruise set to 50-52, and notice nothing.

jnaval

Maybe it's just the way it shifts?

91cavgt

If it only happened when the car was shifting in and out of gears then yeah, that would explain it but what I am seeing is not shifting in and out of gears. It is more like the car going to idle then back to cruising rpm while staying in the same gear. If it was shifting it wouldn't jerk around like it does.

ScionFred

iTrader: (1)

Ding, ding, ding! We have a winner! (My money is with yours)

An additional contributing factor to this might be PPS/TPS related. Having a UEGO (AFR gauge) lets me clearly see how often my ECU enters off-throttle fuel cut prematurely at very light throttle/load (~35mph cruising). This causes the torque convertor to bounce back and forth from accel to engine braking, engaging/dis-engaging TC lock-up, causing drivetrain lash and rpm bounce.

This is not directed to you but some of you guys need to keep in mind that a torque convertor is not a direct physical connection between the engine and trans like a clutch is. It's a hydraulic connection and as such has a certain fluidity to it's engagement/disengagement. RPMs will fluctuate. When you see rpm fluctuate under sustained load, it's time to worry. I probably have the same problem but it's really the least of my concerns presently.

elwaylite

iTrader: (1)

Thanks Fred, that helps. When I really started noticing it, thats what I felt it was trying to do was engine brake, because it's done that plenty on hills, but it would kick out REAL fast (decel/accel). Made me wonder if something was wrong, but the more we look at it, it may just be the way it is.

I never thought it was slipping, because Ive had a slipping clutch before and thats a whole nother feelin.

RC-PILOT

You said it before I could. This really sounds like a computer control issue not a mechanical or fluid issue. I am sure they will figure it out soon enough. All mfg's have computer updates available to fix stuff they never encountered in there lab tests. PLEASE keep us posted....

natesi

So, the new transmission fixed the 3rd to 4th slip, right?

strtrcril87

Mine has the slip going to 4th...it sounds like most of the comments in this thread are talking about why it shifts up and down constantly at low speeds...drop it into the sport mode so it won't be constantly shifting to 4th.