Matching a TH400 to my truck

[Gyoas759]

Okay. It looks like I'm going to need to replace my transmission. I have been shopping around on Craigslist and there are a number of TH400s available. What do I need to know to make sure I can install it on my truck? I have an 89 3/4 ton suburban 4x4 with the 350 V8. Would of course prefer to find a direct swap.

 

[YZEATER]

you need to know what t-case you have. should be a 208 or 241 , i think. crawl under there, wipe off the red tag on the back side, and read the numbers.

 

[dremu]

1989 should have NP208. I don't remember if the spline count is the same for the NP241 used in 1990-91.

At the very least you'll want to get a TH400 out of a 4WD truck; the 2WD ones have a different tailshaft for a yoke instead of bolting up to the transfer case.

Your ideal donor would be a similar year (late 80's through '91) 3/4 ton Burb or pickup, which would be identical (again assuming the NP208 and 241 share inputs, which I *think* they do.)

In theory most any 4WD version would do, but I seem to recall there being different lengths of tailshaft, which might bite you in the butt.

Also, unless you really trust the guy you're buying the replacement from, just getting yours rebuilt might not be a hell of a lot more. I think I paid six or seven hundred bucks for a good local shop to rebuild mine (I did the R&R, just delivered the tranny to them bare), so it might be worth a coupla hundred bucks over buying a random used one.

-- A

 

[diesel4me]

I am pretty sure the 4x4 version of the TH400 only comes in one configuration,and all of them had 32 spline output shafts,unless someone swapped in an aftermarket 27 spline one..its the 2wd ones that had a miriad of tailshaft length variations..

 

[obijuan]

there is a post 85 output shaft and a pre 85 shaft. this is for 205 tcases for sure.

left is post 85 round pattern and right is pre 85 figure 8 205. i dont know if this transfers over to the 208s though.

 

[Gyoas759]

Okay. I double checked and my T case is a 241. I have sourced a good used transmission from an 86 4x4 dually but it has a 205. Can anyone confirm whether or not this will work. Do I need to find an exact match to my t case?

 

[obijuan]

that should work fine. it would be the one on the left with the short shaft, i would just double check that to be sure.

 

[onetonbb74]

the one on the left is the one you need, it has a shaft stickout of 2" for the 208/241 version.

 

[Gyoas759]

the one on the left is the one you need, it has a shaft stickout of 2" for the 208/241 version.

So does this rule out the trans with a 205? Am I understanding correctly that a trans with a 208 is interchangeable with a 241?

 

[obijuan]

no just before 1985 the 205 used a different shaft. after 85 theyre all the same.

so if it is indeed an 86 4x4 trans it will work.