Any input is appreciated!

'95 SE Auto, 223K Miles, Original Tranny

The fluid is full and is still a bright red color.

From first to second and second to third it shifts beautifully 100% of the time. The issue I'm seeing is only occasional, seems to be only when the transmission is cold, and affects 3rd and 4th.

The only times I've noticed it is leaving my driveway and accelerating to 40 MPH down my relatively flat road. When I hit 40 and let off the gas a bit, it kicks into 4th as normal, RPMs drop to around 1300-1400 as always. The trouble is, it'll immediately drop back into third, then back to fourth after a second or two, and it will repeat this for the distance of around a quarter mile if I maintain the same amount or less throttle. If I step on it a little harder, it stays in 3rd. If I let off completely, it still switches back and forth between 3rd and 4th until it coasts down to a speed where it wouldn't be in 4th anyway. If I turn overdrive off, the issue goes away completely, because then it doesn't try for fourth.

It's done this twice to me, the first time I almost didn't notice because it was gentle and I was maintaining a constant speed--I just noticed the slight lurches and the RPMs changing from the shifts. This morning, it was a bit more violent...almost like a soft thud when it drops back to third.

When it's warm, it hasn't done it...and after a mile or so, it behaves perfectly okay...picks the right gears, drops down a gear if it needs to climbing a hill, goes into OD if it has a chance, floor it and it'll drop to the lowest possible gear without overrevving and shifts smoothly under both heavy and light acceleration.

Any advice as to what to do/what not to do to try to prolong the life of this transmission or even solve this issue? Thanks!

 

Check the TPS, make sure the sweep is clean and linear.
Vehicle speed sensor working OK?
Any CEL?

 

jas--

This may not help, but I've had a similar issue. I get the same behavior at freeway speed, under light throttle. The tranny will go back and forth between 3d and 4th. Also, if I let off the throttle completely (going downhill) it will often drop out of gear, down to idle speed. If I give it throttle it will go back up to normal engine speed. It's sporadic--sometimes it's fine, and sometimes it will just start doing it. I haven't noticed any correlation to engine temp. Like you, if I turn off OD, it's fine.

I assume at least part of the problem is in the torque converter, and maybe in the OD circuit or gearing. At first I though the tranny was going on me, but it's been going on for about 7 years now. Early on, I replaced the TPS, but nothing changed (and the new TPS tested fine). And it's not throwing codes.

 

How would I go about checking the TPS? Just seeing if the engine responds to the positions on the gas pedal as it should? If so, it doesn't have any hesitation or anything like that--engine seems to respond to the throttle exactly as it should?

If the speed sensor has an issue, it hasn't thrown a code for it. My CEL is on for 03 02 (EGR Flow), but I just checked it again and that's the only code it's throwing at the moment.

That definitely sounds pretty similar to my issue. It is only under light throttle, but so far it's only been in the short distance right after I start the engine. Mine hasn't dropped out of gear when I let off yet, but it continues to shuffle between 3rd and 4th. If I give it more throttle or turn OD off, it's fine. Sometimes when it's warm, it won't do the shuffling between gears thing, but it almost seems as if sometimes the RPMs change within the same gear at a constant speed without touching the gas (using the variance within the torque converter?) but I haven't really noticed/watched this enough to confirm it. I'll keep an eye on that, though.

I'm worried too, that my tranny is about to meet its maker, but the more I read, the more I'm hopeful that's not the case. After all, it still shifts smooth as butter otherwise, doesn't go through any fluid, and the fluid looks like it just came out of the bottle--it's just this one occasional quirk. All the vehicles I've seen transmissions fail in before acted totally different (a 93 Jimmy was by far the worst--it quickly went from perfect to almost undriveable--wouldn't always go into gear, if by some miracle you got it into gear and managed to get it to shift from 1st to 2nd, good luck ever getting it out of 2nd again, etc.).

In general, I guess my next step sounds like the TPS--what should I do to check this out?

Thanks for all the input!