Hi Guys,

I did a search for this so I wouldn't have to ask the question, but I got over 5 pages or results and most had to do with specific questions on it which were for the most part to technical for me to grasp. So I am asking it here.

Anyway, I have an '86 IROC sitting in my garage that has been there for 3 years because of a bum transmission (TH-700-R4).

A buddy of mine is getting a Van with a recently rebuilt TH-400 Tranny that he doesn't need (he is parting the Van out because he just needs the engine). He told me I could have it for $100.

I have a couple of questions....What other parts are needed to swap the trannies? I heard mention of some sort of kit from Jegs. I can get my 700-R4 rebuilt for $900 including labor, would I be better of doing that?

Also, which transmission do you think is better overall? Is the TH-400 4-speed (I would have known that a few years ago when I was a regular on this site, but have since forgotten).

So basically I am just wondering what would be best to do. Please keep in mind that I will also have to pay labor for everything because I can't do it myself. Thank you very much.

-Josh :hail:

 

The TH400 is a 3 speed trans, no overdrive. From what I remember the 400 is 2 inches shorter than the 700. This will require a longer driveshaft. The crossmember mounting is wrong as well, requiring a refab or kit from B&M, etc. You will probably be better off rebuilding the 700 from a money standpoint, unless you need the beefiness of the 400.

 

Ahhh...Thank you, that is the answer that I was looking for.

Take care.

-Josh

 

hey ricktpi,
if it is cheaper to rebuild the 700r4 then how come the 400 is cheaper new than the 700r4. is it just becasue of the overdrive because correct me if i am wrong but wont the 400 take more abuse? so why is it cheaper? i am just askin on athe standpoint of rebuilding over bying new for any vehicle. since i know about the extra expense of driveshaft and the conversion kit.

 

You'll also need a slip yoke for a TH400. Your 700R4 slip yoke will fit every other GM tranny. The TH400 has a larger output shaft. The tranny out of the van will have a bolt on yoke. You need to remove it and install a slip yoke.

If you really want an OD with the TH400 you can buy a Gear Vender OD unit that attaches to the back of the tranny. It's heavy and requires an even shorter driveshaft but it can be done.

The swap kits should include everything needed for a typical swap. They deal with the crossmember position, torque arm mount, downshift parts etc.

 

spartyon,
If you read the original post you should note he said that he would have to pay someone to do the work for him. If you have to pay someone to do custom work it can get real expense, real fast, thats why I suggested rebuilding the 700. If he could do the work himself it would be much cheaper & would make the 400 swap something to consider.

 

hey rick disregard his post for a min. i was just wonderin why it is cheaper in jegs or summitt to get a rock hard 400 as opposed to a 700r4. i was assumin just the overdrive feature, right?

 

Why not click the link up top from sphon, get the TH400 crossmember and Torque arm, then get a driveshaft cut? You need a short tail shaft TH400.