TH400 transmission rear seal leak
 

I started filling the TH400 in my '60 Catalina and the rear seal started leaking. After crawling under the car, I could see that the transmission yoke (original '60, IIRC) was significantly smaller than the rear seal lip. I don't know why I didn't notice that earlier--I guess I was more concerned about whether the driveshaft yoke splines fit the TH400 output shaft splines (they did). What should the outside dimension of the driveshaft yoke be to fit the rear seal? I measure the existing yoke at 1.688". Anyone know the usual dimension for the yoke? It looks as if I'll have to remove the driveshaft(s) and replace the yoke. I wish I would have noticed it when I had it in for shortening.

Thanks in advance for any info.

Jim

Not knowing what year your TH400 is, I picked '68 Bonneville and looked up the seal on Rock Auto. They list two parts. One is an SKF 15041 which has a shaft size (ID) of 1.5" and a OD of 2.381" There are about a gazillion alternate/OEM part numbers for this seal. This isn't what you need.

Then there is a L&S Automotive Products part # 7116871 'A/T rear seal 1.687" shaft'. They don't list the OD size, but this may be what you need.

i believe there is a thick and thin yoke for the 400 turbos

So, can I just replace the seal and not the yoke? That would be a lot easier, assuming the smaller yoke would be strong enough for occasional racing.

Jim

I would double check on that
it sounds too easy

You're right. I just talked to Hughes Performance and he told me there's a bushing inside that will be too large as well, so I have to change driveshaft yokes.

Thanks for your input.

Jim

I took the shaft in today to have a new TH400 yoke put on with an adapter to adapt the new yoke to the '60 driveshaft (a u-joint with two ears for the TH400 yoke and two ears for the driveshaft). The driveshaft will have to be rebalanced, but at least it won't have to be shortened again. The TH400 yoke was a little longer than the original '60 yoke, but it will still work.

I'm glad I discovered my screw-up before I drove the car. It would probably have torn things up pretty good.:eek:

Jim