hey guys, so ive been dealing with this problem since i bought the car, anyways. its an 86 iroc-z. basically the problem happens when the car warms up. usually if its still cold, it will only jerk slightly, but once fully warmed up, it almost makes the tires chirp, if your not fully pressing the brake. but anyways the problem is its worst when going from Drive to Reverse, but it happens from Park to any other gear aswell. heres a list of things ive replaced which i would think would help the problem, but i havent really seen much of a change.

New rear brake calipers (4 wheel disc)
Rebuilt transmission
New Torque arm bushing
transmission mount
adjusted the Engine Idle speed and TPS

i really dont know what else to suspect, i really thought fixing my idle speed woulda helped, it used to idle around 1100 to 1200 in park, now i got it to 850. also the rear calipers were not working, but even with the new calipers and the parking brake on, the car still bucks rather hard.

this leads me to believe it could be an engine motor mount. any input is welcomed, thanks

 

Check all the mounts--
motor, trans, torque arm, lower control arms, & U-joints.

IDK how to check torque converter. But if it is a temperature related thing, then my would be torque 'verter. Is it a stock 'verter? Performance valve body?

Trans fluid level ok? Fluid red or brown & smells bad?

If you're @ 850 RPM in P, what are you at in gear?

Yea basic, but that's about all I can think of.

 

Have you checked the u joints?

 

yeah. all the normal transmission stuff is fine. fluid, new torque converter, stock valve body, vette servo. new torque arm bushing, u joints are fine, tranny mount is fine. and sorry, i meant the car is around 850 while in drive

 

I would set the idle to 550/600 RPM's for auto. No wonder @ 850 it jumps on you.

 

Mine is exact opposite but I KNOW my trans is out the door. To many overheats while driving. When cold it jerks hardcore from any gear to any gear, but big time from park to drive or reverse. When warm its a bit more forgiving. My idle sits where my buddies did and his Camaro NEVER JERKED. Idle around 800rpm when in gear. I dont think idle setting should cause this since it DID NOT in my buddies who's was smooth as heck, cold or warm. Just an experience. I'd check mounts for sure, as I'm sure mine are also done.

 

850 is too high in drive? so i should set it around 600?

 

Yes, set it 550/600 RPM's at idle and the RPM's should drop when you put it in gear.

 

i was setting idle speed while car was in drive. so i should just aim for 550 while in park?

 

i just set idle speed to 650 in drive. the clunking is still the same, almost as if its not rpm sensitive.