output shaft seal for Th-400
 

Hey guys i'm having trouble and i am very confused about this transmission. I cannot find a rear output shaft seal for this 400. the transmission is out of an 86 c10. i've gone to napa, o'reilly and autozone and every rear seal they give me is just barely to big to fit. Whats going on here? I know for a fact this transmission is a 400. Are there any other transmissions that have tail shaft housings that are interchangable with the 400?

2 different seal can be in your 400. If your slip yoke has a 1.875 seal surface use a National# 9449. If the seal surface is 1.687 use National# 7038SA.

i've tried both of those seals...thats why i'm confused.

Is the OD or ID wrong ?

You sure its a Th-400? The Modulator is on the front RH side close to where the filler tube goes into the case?

Can you see any numbers off the old seal? If not,measure the OD of the old seal and then measure the seal surface of your slip yoke and post them.

i will post the numbers and the diameter of the seal within the next couple hours. its for sure a 400 judging from the pan shape and length of the case.

tranny ID
 

That would be #4 right?

what are the other ones in the numbered pic?

Look about 3/4 way down the page here>> http://www.maliburacing.com/auto_tranny_id.htm

Check the Spline count on the Output Shaft. Is it 32-spline or 27-spline?
TH400 has 32-spline count, TH375 has smaller TH350 size 27-spline count and a TH400 pan shape, the bushing is smaller on the TH375. It will have a 9-1/2" tailhousing also.

"" A medium duty version of the TH-400. On the underside of the trans, right where the tail housing bolts up, the letters "TH-375" can usually be found cast into the trans housing.""


From here:
http://www.442.com/oldsfaq/oftrn.htm...n%20Comparison

http://www.442.com/oldsfaq/oftrn.htm...Identification