dlove

iTrader: (23)

well i got a th400, or so I though for free. But it turns out it's the HD version.

What all is different?

I have a B&M racing overall kit that i was going to use. But now I dont know if i even want to bother since it is the HD version. I started to change some of the seals and **** and found out the output shaft is 27 spline! So it will work with my stock yoke. But, the seal in the kit was the wrong size.

The clutchs and steels all look great. Except for one broken "flex" steel (the one on the very bottom). Is this the same as a non HD one?

What all is different, should i hold onto my extra clutchs and run the ones in the tranny?

teach me something about this tranny!

dlove

iTrader: (23)

I found that the thm475 comes with straight cut planet gears and stuff. But mine are helical cut...

It is a HD version, the big HD cast into the case kinda is the dead give away.

Does anyone know anyhting about this tranny!?

performabuilt

iTrader: (25)

Ok what you have is basically a H400 with the TH350/700R4 splined output shaft ,I would have no fear of using it since from and build perspective and durability it should do just as well . They 400 kit you have should work except for the tail housing seal with is the same as a th350

dlove

iTrader: (23)

this is not a TH375, as the th375 is clearly labeled that under the tail shaft. Mine does not have that label.

Also, i dought it is just a th400 with a th350 tailshaft. The case has a big HD rasied in it on the bellhousing. It also has the id tag of LJA which is known for being the HD version.

The flex steel im referring to might also be know as a wave steel I think.

performabuilt

iTrader: (25)

Take a pictur of the trans and the part your speaking of and send it to performabuilt@yahoo.com and ill tell you exactly what it is. But with the 27 spline tail thats the only 400 Configuration I am aware of

8a8mfh

iTrader: (3)

I found the same thing in a 1988 2500 GMC Sierra. My friends dad got it brand new in late 1987 with 14 miles on it. The transmission was never out of it.
I bought it off him in '02, went to rebuild the trans and found exactly what you have, HD on the top of the case, no straight cut gears, 27 spline output.
Some random things---I buy my rebuild stuff seperate, the gasket and seal sets I get usually have both rear seals and both rear bushings. I am not a pro trans builder I do it on the side but I have yet to see a set of straight cut th400 gears. I've rebuilt several motorhome transmissions, I have a few cores that came out of one ton trucks, no straight cut gears.
The one ton and HD th400's like you have there have the same exact seperator plate used in B&M th400 shift kits.
There are more than a handful of guys especially on 454ss.com who will argue all day long that these 27 spline th400's are th375's, they are not.
Like I always tell them, if you do a high performance, heavy duty rebuild on a th375, th400, th475, they all come out with the same parts. Order a rebuild kit for a th375, it'll come listed as rebuild kit GM th375, th400, th475.