Transmission partially slips when hot, but shifts perfect after restarting engine?

[Abbondanza]

I have recently replaced a failed transmission in 96 v6 XLT, and it shifts great when starting out cold, however after getting completely warm and stopping for like 15 minutes, after starting up again it will slip in 1st and 2nd gear, not a complete slip, but high revs and slow movement.

If I pull over and shut off the engine, then immediately restart it, it shifts great again.

Anyone have any ideas what would cause this symptom?

Thanks.

 

[Tedybear]

If this is a salvage pulled transmission I'd say it's a dud.

Probably not the news you want to hear, but it sounds like pretty bad pressure control issues.

When you changed out the filter upon install how did it look? Any metal shavings in the pan or on the magnet?

S-

 

[Abbondanza]

Thanks for the reply.

I don't think the tranny's a dud, because it shifts strong and smooth all the other times except for the when it's hot and I do the quick stop and start again shortly thereafter. When I changed the filter the pan and filter were completely clear of debris.

As I said it's not a total slip issue, it's like a revving flare as the car is moving forward but just seems to be in the lower gear too long. Also if I intentionally 'get on it' and accelerate faster from a complete stop, the problem never occurs. It's only when I pull out slow that it may happen.

I read it could be the trans valve body plate gasket failing that would cause this or possibly the torque converter.

I'll start with replacing the valve body plate/gasket to the updated version and see if that helps.

Thanks again.

 

[Tedybear]

Thanks for the reply.

I don't think the tranny's a dud, because it shifts strong and smooth all the other times except for the when it's hot and I do the quick stop and start again shortly thereafter. When I changed the filter the pan and filter were completely clear of debris.

As I said it's not a total slip issue, it's like a revving flare as the car is moving forward but just seems to be in the lower gear too long. Also if I intentionally 'get on it' and accelerate faster from a complete stop, the problem never occurs. It's only when I pull out slow that it may happen.

I read it could be the trans valve body plate gasket failing that would cause this or possibly the torque converter.

I'll start with replacing the valve body plate/gasket to the updated version and see if that helps.

Thanks again.

Almost sounds like an old school vacuum modulator fail. Interesting... With most systems being driven by solenoids and servo's and whatnots....

Good to know there wasn't a lot of crud Mc'Nasties in the pan.

Be an interesting case study on that one. I'll keep an eye on this. Look forward to updates!

As a side note: I've never had a torque converter outright fail- Not saying it can't happen. If you get on the gas hard for passing gear and it takes off like a bat outta he&&? I'd be less inclined to think converter.. But I've been wrong before...

S-

 

[Abbondanza]

The reason I say it may be the TC is that after assembly I hadn't tightened the bolts to flexpate enough and it was it was literally scraping against the bellhousing because it was back to far.

Then I used an air ratchet to tighten them and wrongly assumed when the wratchet sounded like they where tight I stopped for fear of over-tightening, and the scraping sound went away, but I still got the 'deisel rattle'.

I was pretty spent after doing this tranny swap on my back in the driveway so I drove it that way for about three weeks (noise driving me crazy) until I finally went under there again and tightened them for a third time and the noise disappered.

Maybe three weeks of rattling messed up the TC a bit, although yes under high torque it's great, so I can live with it until I try the separator plate upgrade.