Hi there :

I have a 86 IROC with LB9 (305TPI) 700R4 combo, when i start the car , and i put in Drive , the car make a "little-big forward bump" , obviously not more , because i have my foot on the brake.

I have to add :

New transmission oil , new filter , new pan gasket .
The old oil , dont have a strange color , and of course, wasn't metal particles on it.

Any clue ?

Cheers , JF

 

I forget the exact cause of it but for an 86 700 that is normal. They slightly redesigned them in 87 and onward so that going into reverse or drive didnt result in the car jolting forward or backward. I had an 86 and it did the same exact thing.

 

I have an 84, but with a swapped 81 350 and a yurbo 700 from god knows when. I never got a chance to be sure, but i assumed it had to do with the TV cable being too tight at idle and and the tranny pressure being too high and making it think you were like neutral dropping it. Dont know a thing about auto trannys really but this made sense kinda.

 

the early 700r4 had one of the clutches in the input drum right next to a wave steel. in the late ones the clutch moved behind a flat steel which fit up against the wave. Made for a more reliable clutch life. To make the change they made an auxiliary valve body to cushion the forward clutch apply in the late one using a piston and spring in a housing.
bump in the early might be more noticeable than in the late if you're sensitive. you forgot to mention if it is a new concern or if it has always been there-crucial to be specific.

 

for the nice technically answer.

It happens since i bought the car , and supposedly before , the old owner told me "the tranny is almost gone" , but i dont't trust in that boy , he was a ignorant.

I should check that , and get the year :

http://www.hotrodders.com/articles/T...ification.html

I bet a beer , it's a 86 700r4

Cheers , JF

 

Yeah, i adjusted the TV cable , and the bump dind't disappear! Overdrive is nice (sometimes) , but i'll get a TH350 for my next car.

Thanks for the help , boys! , you're great.

Sorry about my crap English.

Cheers , JF

 

you could do a long th350 for that car. It is the same length as the 700r4 and uses the same driveshaft!!!!!! They are cheap and have the same third gear ratio 1 to 1. As a benefit the car will probably pick up faster as there isn't such a rpm drop into second gear. The only thing the th350 would need is the vacuum modulator hooked up to the intake manifold with a vacuum line. Also it has no t.v. cable. You could just block the kickdown hole with a cut off cable if you didn't want to fiddle with hooking it up. sounds easy eh?

 

ok, i have this same problem, but also mine will pretty much slam into 2nd and 3rd gear. when i say slam, i mean forcibly spin the RR tire going into 2nd, and chirp 3rd. btw, my car is a 1990. came from the factory with a 3.1/700R4 combo, and i know it's the original trans.

 

probably broken 1-2 accumulator spring. it is in the housing that is in the pan. the 1-2 accumulator housing is held in with 3 10mm bolts(not to be confused with the forward housing 1 8mm, and 2 10mm). replacing the spring might help. also the t.v. might be adjusted where the pressure is too high. just some random thoughts.