The slimJim transmission in my 1957 Oldsmobile (previous owner replaced the 371 engine with a 1963 394 engine and slimjim) seems to be leaking around the speedometer cable shaft. I replaced an outer O ring but it still seems to leak. Is there another seal inside that needs changed? I also think there is a small leak from the output shaft. Is Fatsco the best place for these parts? Thanks in advance.

 

I'd think the speedometer cable might be faulty. It looks like there's RTV slathered into the cable in an attempt to fix the leak. Start by cleaning everything thoroughly with brake or engine degreaser so you can pin point the leak

 

Thanks for the suggestion about the cable repair. In regards to the RTV, I tried that. Originally when it was leaking out of the speedometer cable connection I replaced the outer O ring. It still leaked down the cable. I tried putting some RTV on it to slow the leak...but it does not help. I remember another person telling me there was 2 O rings in there (an outer ring that I changed and an inner ring). I think that was a forum member named @Charlie Jones

 

If the speedometer is driven off the back of the trans it is either a '61 or '62 trans.
Here is an illustration of the '61 trans. Note #4.337 is the speedo gear .
I believe that the three "O" rings #4.338 seal that speedo gear unit from leaking.
The larger "O" ring would go in the groove in the body of the speedo gear sleeve .
And the smaller two should go inside the sleeve to seal the gear.
Hopefully you can find these at an automotive or industrial supply store.

 

Thanks so much for the diagram. Looks like I need to change 2 more O rings. Thanks again.

 

You may also need to replace the output shaft seal #4.318
FATSCO should have them.

 

Thanks again to everyone for the great information.

 

Just checked the Fatsco website for the SlimJim Roto 10 and I don't see an output shaft seal listed. I also only see 1 seal listed for the speedometer cable. I did change that one but don't see any other listings. In the picture above it looks like 1 large O ring and 2 small O rings.