TH400 Swap

[a.boddie.matthews]

i have an 1988 Chevy Monte Carlo SS. SBC 350 with a 200r4. The transmission is blown and Ihave a th400 that I want to swap in. I would like to have a driveshaft made prior to install so that once the swap is done, I can begin driving rather than having to wait another couple days while the driveshaft is being made. Has anyone ever done this swap, and if so, what is the length of the driveshaft for this conversion?

 

[gbody4life]

Just to put my two cents in for what its worth but if the Trans in it now in blown doesn't sound like your doing much driving in it anyway. Your better off doing the swap and then taking an exact messurment because everbodys set-up may be litle diffrent even by an inch or two and that will make a big diffrence. There are certain things you want to account for most importantly motor mount placement could be diffrent in each car. Even though all g-bodys are alike you can never be certain that yours is identical to someone else's, especialy considering they could have been built in two diffrent factorys. If you get a measurment from someone and when they put their motor in theirs maybe sitting an inch or two forward or back. I would hate for you to spend 400.00 on a new driveshaft and it's an inch too long. I would just do it right and be patient

 

[just plain john]

I agree. Get the trans in first. If you're doing it yourself and have the proper tools, it's a couple of hours deal. Find a reputeable driveshaft shop locally and ask their advice. I'm sure they will ask you to give them a specific measurement, and will tell you exactly how they want you to measure it. In my case, it was from the face of the rear of the case to the parting line on the pinion yoke. Your shop may measure it differently. The aftermarket crossmember vendors advertise the same part number working on both (http://www.crossmembers.com/g-body.htm). Assuming the xmember doesen't move could you measure from the mount to the end of the case on both transmissions? I would think that measurement would equal the amount to be shortened.

 

[Blake442]

I'd rebuild the 200-4R instead, unless you've got a wild *ss motor that would require a 400.
You'll miss the overdrive, that's for sure... I know I do...

Assuming it's a short tailshaft TH400, the overall case length is a 1/2" longer than a 200-4R.