Size of tail seal

[chromebumpers]

I went to NAPA today to pick up a seal for the end of the transmission. I didn't think it would be a big deal - a garden variety TH400 right? Nope! they list 2 and vastly different sizes. I don't have the old one out yet, I don't like starting something and then looking for a part. If anyone has the correct NAPA part # , or the correct size in mm it would be greatly appreciated.

PS, they're really cheap - $2.50 and $2.80 for the larger size.

 

[grumpyvette]

this is where having a decent set of dial calipers handy makes getting the info you need easier, and having a 12 ton hydraulic press to disassemble u-joints sure won,t hurt

the problem is they made several versions and the truck version of the transmission usually had a different tail shaft and drive shaft yoke

 

[chromebumpers]

My truck is using the lift this weekend, I'm fabricating all new brake lines and it's a bear of a job on this truck weaving in and out and around so many bends and turns. Anyway, since I was at NAPA already I thought about some other repairs coming up soon. I didn't pull drive shaft out yet and I didn't think there could be other sizes (not on a std. coupe Automatic 400)

And I do have a caliper and a 20 ton press.