I had a brain wave today while resealing a transmission. I've pulled out so many speedometer drives that are slathered in RTV trying to stop a leak. But that o-ring at the top of the drive almost never does a good job of sealing, even when new. Part of the reason is that the speedometer cable hangs off the end of that thing and vibrates back and forth, eventually wearing that bore into an slight oval.

It occurred to me that adding a second o-ring further down the drive body would help by adding another level of protection as well as helping to keep the drive centered in the bore, thereby helping the upper o-ring to do its job more successfully.

So that's what I did, and if anyone else is interested in having this modification done, check here.

great idea , could you have done it ahead of the bolt ? your method may still weep at the bolt.

Very cool! Or either side of the bolt. I think this will definetly be sufficient though. If you need a test subject for a 3 O-ring setup I will volunteer!

Cool!

I'm still trying to remove one of those from my spare transmission.
I can get it to move about .040 with a lot of pressure and that's about it.

Got a slide hammer? I have a 911 speedo cable 'stub' that I could make into something compatible with the slide hammer. That'll get it out.

Great idea.... now drive the transmission 50,000 miles and tell us how it does...

I like it, repost when you get the other seals..

I've confirmed that the seals I ordered are the correct ones. This modification is now only sold as a complete refresh of the speedo drive. Two new o-rings, a new internal seal, and a new sealing washer. All new, through and through, and better than original.

Ordered mine and sent off a core today.

Interesting. I just clean up the bore and use Vaseline on the seal. I am interested to hear how this performs, but your logic seems solid

Mine was leaking a few drops a day. I folded up a shop rag and zip tied it around the drive. That was a 2 years ago, haven't seen a drop on the floor since, and I like how cheezy it looks.