My 700R4 is getting weak and everyone is telling me even the built ones wear quickly at the track. I have always had good luck with the TH350 and wondered if it is a somewhat easy swap into my 89 GTA??? I was told that someone made a direct fit x-over but the driveshaft was too short? Is this even a good idea and if so what else needs to be done for proper fitment and driveshaft angle ect..thanks

 

Do a search on this topic and you'll find tons of info on it I as I have personally contributed many times on this subject-forewarning: it'll be the easiest trans swap you'll ever do.

 

If you can find a th350 with a 9'' tailshaft you won't need to get a new driveshaft.

The main problem with this swap is the torque arm mount. The th350 doesn't have one. You can spend 375$ and get the spohn th350 swap crossmember/torque arm. This is a nice piece but pricey. It would help with traction and be much stronger.

All you really need is a crossmember/torque arm and a new driveshaft if you get the short 6'' tailshaft th350. And a new TC of course.

Im also thinking about doing this swap.

 

Yea, Spohn is going to make this easy. I may even do the 400 swap as all parts are available and not much price difference on the tranny....
thanks!

 

With the '89, don't forget you have a magnetic vehicle speed sensor in the TH700's tailshaft...which the TH350 (or TH400) won't, it's a gear-driven speedometer cable design.

Kiss your gas mileage goodbye ...the 350 and 400 have no OD and no locking torque converter.

Jags That Run (jtr.com I think) sells a translator that screws onto the TH350's gear-driven sending unit and makes this pretty painless.

B&M sells a TH350 swap kit that handles the torque arm mounting, just another option. Not sure if it'll work with a TH400.

Personally, I'd either go with a TH400 swap in a T56 manual trans.