Besides the torque arm what is needed to swap a 350 turbo or 400? Will the stock crossmember even come close to fitting? I need a trans built and going to buy a converter anyway so I may just swap to a 3 speed and not worry about breaking it.

 

i believe you will most likely need a different driveshaft depending on what length tailshaft the trans is. Im sure you could fab up a crossmember for mounting the trans but it would be easier to just get one from spohn and not worry about it.

 

Swapping out a 700R4 to a TH350 is very simple. The conversion kit makes it a simple swap. The kit provides everything needed. You need to remove the 700's TV cable and install a TH350 detent cable and you need to run a vacuum line down to the modulator.

Swapping to a TH400 is a little bit harder. A different crossmember is needed because of how far back the TH400's mount sits. Because the tranny is much longer, a shorter driveshaft is needed. You also need a new slip yoke. The TH400 has a large diameter output shaft than all the other GM automatics. The TH400 uses an electric kickdown so a switch needs to be installed on the throttle somewhere. Because of the extra length of the tranny, mounting the stock torque arm means some fabrication work. Using a Spohn torque arm and tranny mount makes the swap easier.

The difference between a TH350 and TH400 converter is the position of the 3 mounting bolts. The majority of all the aftermarket flexplates will have dual mounting patterns so it doesn't matter which bolt pattern you buy the converter in.

 

Thanks, Stephen. Who markets the kit for the 350 swap?

 

http://www.jegs.com/webapp/wcs/store...0531&langId=-1
http://www.jegs.com/webapp/wcs/store...0531&langId=-1

Oh look, Hurst also has a TH400 swap kit.

The TH350 swap keeping the same driveshaft depends on what TH350 you get. The long tailshaft TH350 is 9" long and can reuse the 700's driveshaft. If you have a short tailshaft which is 6" long, you need the longer driveshaft from a third gen that had the 200c tranny.

 

Looks like I can use the stock style torque arm with that Hurst kit. Hmmm. Thanks for the links