ok guys its been a long time in the making but i cant put it off anymore what all am i going to need crossmember driveshaft torque arm???? i would love for someone to tell me the 4th gen alum driveshaft will fit but im sure itll be to short

 

you can get a long tailshaft th350 and use an adapter for the tq arm. You then can use the stock crossmember and drive shaft.

If you cant find a long tailshaft th350, then you can buy a extension kit. It involves changing to a 700r4 output shaft and tailshaft. It will make the th350 long enough to use the stock crossmember and driveshaft.

Search the board for the part #'s. The conversion will be easier than finding the long tailshaft turbo.

 

i know the th350 will be stronger but will my car slow down also i have a prostick shifter do they work ok i know the ford c4's are very picky on shifters not sure if these trannies are as well

 

Swapping from a 700R4 to a TH350 is very easy. The swap kits make it a driveway job. The kit includes a mount relocation bracket for the torque arm and a relocation plate for the tranny. You'll need to use a long tailshaft TH350 to reuse the original driveshaft or the 4th gen driveshaft. If you use a short tailshaft TH350, you'll need a driveshaft from a 82-83 third gen that came with the metric 200 tranny (3 speed)

Aftermarket shifters come with proper brackets for the shift cables that will adapt them to different trannys. I originally used a B&M Megashifter but didn't like it for drag racing and have switched to a ProRatchet.

With the TH350's 2.52 first gear you won't be as quick off the line compared to the 700R4's 3.06 however the TH350's gear ratios are closer together so the 1-2 shift will keep you in the powerband more and should make for a quicker pass.

The TH350 is also lighter and doesn't have the extra moving parts of the OD so less HP is lost through the tranny.

 

not trying to hyjack. Do you think going from 700r4 to a th400 will slow the car down any?

 

Difficult to say. The gearing is better. The TH400 has a 2.48 first gear and a 1.48 second gear so it's about the same as the TH350 but still better than the 700R4.

When you tear the trannies down, you can see why the TH400 is so much stronger. Internally it's just much better designed for lots of torque.

The TH400 is big and heavy. It weighs about 130 pounds. While the TH350 uses up about 36 hp, the TH400 uses about 44 hp. My powerglide uses about 18 hp.

I wouldn't recommend a TH400 unless you have a very heavy car (3500+ pounds) or you produce well over 500 pounds of torque. Spending the same amount to build either a TH350 or a TH400, the TH400 will survive longer. Performance parts for the TH350 are expensive because the tranny isn't designed for a lot of abuse. You can pull a junkyard TH400 and add a few factory parts to have a strong reliable tranny. Doing the swap to a TH400 will cost a bit more. You need to relocate the rear mount back because of the tranny mount location. You also need a TH400 slip yoke for the driveshaft because it's larger than any other GM slip yoke.

 

Cool thanks. I am on a tight budget. A th400 seems like it can take more power for less cash. I run 11.50s on motor and plan on using a little spray out of the hole. How strong is the stock drive shaft? I have been running 1.6 60ft. I have just been waiting for it to break.

 

The steel driveshaft can take more abuse than most people think. The factory aluminum driveshaft is a street only item.

It's not the driveshaft that usually fails but the small, weak u-joints. Get a 3" steel driveshaft fabricated with 1330 or 1350 series U-joints. A standard footbrake launch with an automatic isn't bad. It's when you start using a transbrake that driveline parts need to be much stronger.

 

Slow86 you have my # call me you will be fine with the th 350 and if you have to have a 400 I think I can find one for you. And I was not kiding when I offered to loan you my 1 3/4 headers

 

thanks stephen Im just waiting for a convertor now

 

aahhh. I am the proud owner of your evil twin. Ill be in touch. I havent been doing any work on the car lately. I have been working on getting a better paying job. Thanks again for the help with my exhaust. :hail: :hail: :hail:

{mod edit} fixing quote

 

ok what do you measure to determine if it is a long or short shaft and what would the measurements be thanks in advance

 

If I recall, The TH350 came with 3", 6", and 9" tail shafts. You should be able to measure from the end to were it bolts to the housing. Most trans you find will probably have the 6" tailshaft.

 

I don't think I've ever seen a 3". My guess would be that the 3" tailshaft is a 4x4 tranny that has the transfer case bolded to the back of it. Normally all you'll find is the 6" or the 9".

The measurment is from the back of the tranny to where the rear section bolts onto the tranny case.

 

Yeah, I think the 3" is a 4x4 unit. The 6" units are the most popular locally for me. I have found one 9" turbo "that I can buy" locally.