Hi everyone,
I have yet another problem with my IROC. Its got the 700R4 and I've been having this problem for a little while now. My plan was to bring it to my local tranny shop and have them work on it but if you guys could tell me what to do then it would save me money. This only happens when the car is up to temperature. If im going over 45 mph and let off the gas the tranny grabs it and slows down the car (think letting off the gas on a manual tranny car). Then when it slows down enough the tranny revs the engine up and lets go revs up and lets go. its only about does it beween 1000 and 1500 rpms and fluctuates between those numbers. Then it stops when i hit the brake. I know its the tranny 'cause when i hit it into neutral when its doing that it stops. Any help would be appreciated. Thanks

 

Sounds like it's wanting to down shift and/or something is slipping. Going 45 mph +, you should be in OD. Is it down shifting correctly once you hit the break? and actually, this could be an engine problem. This might be what's happening and why i think it's the engine, NOT the tranny.

1) only happens when hot
2) goes away in neutral
3) I've never heard of this problem with the 700R4's or any auto for that matter.
4) It only happens when you let your foot off the gas

I think it might be a pressure loss problem or manifold leak or something to do with something leaking that ain't suppose to.

Here is my logic broken down...

When cold the engine is getting proper sealment but when it warms up something is expanding letting air out or leaking. So when your foot is on the gas you have enough pressure to keep it idling nice, but once you let your foot off the gas it bogs down and will lose speed, like all cars. But because of the leak it doesn't have enough pressure or something to keep the tranny at a good RPM, so it bounces depending on the leak (how much/where/what) Then when you put it into neutral it goes away because the engine no longer has to put torque on anything so it can idle off of the other pistons that aren't leaking (i think it's a piston/head leak).

Have you floored it and have you felt any noticeable loss of power lately?

 

I don't know that its the engine. The engine has tones of power for what it is. Ive already had a reputable tranny shop take it for a spin and he noticed what i was talking about. he thought that it could be something that controls the lock up of the tranny. Im not sure that that is exactly what he said seeing as how this was awhile ago. It almost feels like the tranny is engaging and disengaging from the engine. Its a really wierd feeling and is quit annoying to drive with. Ive been learning to keep my foot lghtly on the gas at all times when driving and when i come to a light i just pop it into neutral and hit the brake. But just for curiousity..i do have a slight oil leak on the top of my intake manifold. Could this be a possible cause if it does turn out to be the engine?

 

Torque converter clutch.

 

could also be "searching between drive and OD. a mis-adjusted tv cable could cause this. try putting the shifter in drive and not overdrive and see if it still does it. if it does, torque converter clutch as Apeiron suggested. if it doesn't, adjust your tv cable down a click and see if that helps it.

 

If it looks like old oil and been sitting there and isn't wet like new oil, then you're fine. These engines (TPI, LT1, LT4) seap out oil over a long period of time, my LT1 has a huge build up in the back. 180,000 miles worth...