View Full Version : TR2/3/3A Question on overdrive pinion & bearing assembly for speedo drive

05-23-2018, 01:42 PM
Is this the correct speedometer drive "pinion & bearing" assembly for an A-type overdrive type 61374? It was in the overdrive when I bought it and I am assuming it is correct.

The other question I have, if this is the correct pinion & bearing assembly, what oil seal(s) and/or "O" ring(s) are used on it. The only seal I believe that is currently on it is some sort of rubber seal down inside the hole of the round bearing. I can't see it very well and the only reference I have found for a seal is Moss p/n 520-015 shown under #97 on the overdrive page of the Moss TR3/4 catalog. I'm getting transmission oil into the speedo cable so I believe that seal is letting oil seep past the pinion.
Thanks for the help!


05-23-2018, 02:38 PM
Looks like the right part to me.

To replace the seal, you'll have to find a way to unscrew the threaded adapter. It's a lip type seal, not a simple O-ring; I don't think there is any way to remove or replace it through the hole. BTW, TRF also has it listed under P/N 60247.

There are very thin flats on the sides, but I don't have a wrench that will fit, so I used (gently!) a big EZ-out. Another trick that might work is to use the nut off an old speedo cable and crush it onto the threads; either with pliers or (perhaps better) a block of wood with a suitable hole and sawn lengthwise.

The block of wood trick also works for holding the brass bearing without damage.

Also make sure the vent is open. The stock OD vent is unlikely to clog, but someone may have replaced it with something else.

05-23-2018, 04:21 PM
Thanks Randall! I didn't realize that the bearing came apart. Now I see the faint line where it must separate. I measured the flat sides and I get 15.79mm and .622 inch (slightly less than 5/8 which is .63inch or 15.88mm). So seems as though both 5/8 and 16mm wrenches are a bit too large. I have an old 5/8 wrench that I may grind down thinner to fit the flats behind the threaded section and hope that will do it. I see slots on the back end of the bearing, but I think your suggestion of putting pieces of wood on two sides of the bearing in a vice to hold it would work best. BTW, how difficult is it to get the two pieces of the bearing apart? Also, I'd better check the overdrive vent ...where is it located? Thanks!

05-23-2018, 07:32 PM
I believe there is also a pin that must either be tapped out or broken before the unit unscrews...it's just visible in the picture above.

05-23-2018, 10:59 PM
Yup, John is exactly right. I either forgot, or never noticed that pin. As it happened, I had one sitting on the bench so I decided to take it apart and refresh my memory ... pin sheared off easily with almost no damage, but no doubt it would be best to drill it out instead.

Here's a photo that shows it better. You can see the broken stub sticking out of the main housing, plus the remains in the threaded adapter. The original seal is in the foreground.


The OD vent is on the main OD housing, not far from the plug over the operating valve. This is not the original style vent, but is in the same hole/location.

05-24-2018, 09:01 AM
Thanks again Randall! Really good enlarged pictures. That really helps. I don't recall a vent on my overdrive, so I'll have to try to see if there is one on it. Thanks John for high lighting the pin.

05-24-2018, 04:08 PM
John, Randall, you guys are amazing. Thanks for sharing your knowledge!
Steve Baker

05-30-2018, 01:37 PM
Randall and John, I have a question.... what replacement pin material and what diameter & length do I use for the pin for the overdrive bearing?

On Monday I ordered a replacement rubber seal for the pinion & bearing assembly for my speedometer cable driver on the overdrive. So this morning I decided I should go ahead and take it apart. I could not find anything small enough and strong enough to drive the pin out, so I drilled it out with a #60 drill bit. I used a #60 because 1/16" was too large. The bearing came apart quite easily. I had an old 19/32 wrench and ground down the sides to make it thinner. The wrench then fit perfectly. I clamped the bearing in a vice between two pieces of wood and using the wrench it came right apart. I appears that the pin had been out before because under a magnifying glass I could see file marks on the outside of the bearing where it appears the pin was filed down to be flush with the outside of the bearing. I'm hoping I can get a pin in without having to file it off on the top, and not have it protruding down into the hole in the bearing where the pinion goes. That might be a problem if the pin goes in real hard and flattens on the top from driving it into the hole. Any suggestions would be welcome! Thanks!

05-30-2018, 03:26 PM
#60 is .040", so I might try some .042" safety wire. The hole in mine seems to be a bit bigger than that, so 14 AWG copper (.050") might work better for me. In either case, lay it down on a hard surface first and tap with a hammer to slightly flatten it near the end that goes in last.

But more likely, I would just use a drop of Loctite and let it go at that. Once the speedo cable is installed, that piece isn't going anywhere; so the worst that can happen is it comes off with the speedo cable (which, come to think of it, happened to a friend of mine).

That part of the bore doesn't actually contact anything, so a small protrusion isn't going to hurt. If it's too much, some quick work with a Dremel should take care of it. Blow it out with solvent or compressed air afterwards.

05-30-2018, 05:07 PM
Thanks Randall! I found a real small nail that's a good tight fit. I'll cut it off and flatten one end so it won't go down into the bore. I also like your idea of putting some blue locktite on it. I think the nail should be strong enough.

05-30-2018, 05:58 PM
I've always just used the loctite. So far I haven't had one come apart. I think the original pin was brass, which is why it was easy to either drill or shear off.

05-30-2018, 06:07 PM
Thanks John!