I posted this problem about my '85 IROC a long time ago. I haven't been driving the car so I haven't worried about it. Recently I started driving it again, and now I would like to figure this out.

When I put it in a forward gear it jerks bad. Unless it's in the morning when it's cold, then it goes in as smooth as my firebird. It doesn't do this in reverse. I have changed the tranny mount so I know that's not it.

The car shows the code for rear disc brakes but it has rear drum. If someone swapped on a rear end with rear drum but didn't change the proportioning valve to the drum one could it cause it to jerk like this? Or is the just a tranny problem?

 

check your idle RPM's .. usually it's really high when you
get the dump into gear :\ ...

 

That's one thing I always thought it was but I never could check because of a screwy tach. Now I've got an aftermarket tach, the idle is normal. It's even higher in the mornings naturally, and that's when it behaves the best. After it's warmed up it idles at about 700 and that's when it will jerk.

I think there is one thing about the idle though. When it's warmed up and I have it in park it will idle around 700, I drop it into drive, and it jumps a little before the gear engages. I can't remember if my other car does that or not(haven't driven it for a few months).

 

My 89 Formula does the same thing. It is just one of the querks of the 700R4 trans i believe. I think the reason it doesn't clunk into gear when its cold is because the fluid is very think and doesn't move through the trans quickly.. therefore becoming much softer. Email probuilt in the trans forum, he would know.