need advice- TH400 extension housing seal

[brutus]

I'm replacing the extension housing on my '72 C20 because it is cracked. The replacement housing I got has an O-ring groove on the mating surface. I've been looking allover and can't find any reference to the TH400 short tailshaft housing taking a large O-ring to seal, only the thin paper gasket which I already have in my seal kit. Other than that the housings look identical- both large "C" castings.

Anyone have any experience with this? Did GM switch to an O-ring seal on newer TH400? If so, anyone have the part # on it.

Thanks

[TBONE1964]

If your replacement housing has a groove for an O ring then the gasket won't work. Use the O ring and you will be fine. I have never seen one with a paper gasket. The last one I rebuilt was a 1969 trans out of a 69 Chevelle and it had an O ring.

Sorry, I dont have a part number but here is a ebay link for a short style

http://www.ebay.com/itm/N-O-S-TH400-...3146fc&vxp=mtr

[brutus]

Thanks for the info.