Howdy, I am having trouble with the internals of the 4 speed manual transmission that I am getting ready to put back in my car. It is an older euro trans out of a w115, but should mate up to an om617. Months ago I pulled the rear cover off to fix a broken tab that holds the speedometer cable into the transmission and I am just getting back to putting it together.

It is a pretty simple mechanism and consists of a small shaft, a gear that ride on the shaft, and a ball bearing that gets pressed in last to seal it all in.

Here is the rear cover and the slot the gear falls into.



Here is the shaft, gear and ball bearing laid out how they go into the case.



And here is the gear in the case with the shaft.



The problem I am having is that the gear is loose on the shaft, and I believe the shaft should press into the gear. Otherwise, the speedometer cable won't turn. I ordered a new shaft and gear from germany and only the shaft was available. The new shaft fits the same way, and neither of the old parts look worn out.

I am looking for somebody that has some experience with this. It almost seems like there is a piece missing or something. I bought the trans used so I don't know it's history. I just don't want to put the trans back together without the speedometer working. I have a small machine shop if I need to make something specific.

Please help!

You are correct, the shaft should be a press fit into the gear. Two possible solutions come to mind:
1) If the fit between the shaft and gear is less than about .005", Loctite Stud & Bearing Mount will bond them together. The parts will have to be thoroughly degreased, and the assembly process will be a bit tricky.
2) If the gear is not too hard, it could be bored to accept a sleeve with a smaller ID that would be a press fit on the shaft. The sleeve would be bonded into the gear with the above Loctite.

Awesome, thanks so much. This is kinda what I figured but I wanted to hear from someone else on the subject. The gear is quite hard, I think I remember checking it with a file and it just slid across it but I still may be able to bore it. I haven't measured each part but I would guess the runout is more than .005 just by the feel. Thanks again Frank!

Could it be that the gear is tapered and you need to turn it over and try it on the shaft? Silly maybe but a thought.

Got the gear bored out, and a sleeve pressed in then I bored that out to .001" under the shaft size (.355"). Got the gear installed and shaft pressed in. The gear was not hardened

The gear ended up having .006" of runout on the shaft, I am not sure how that much wear would happen and still have the parts look new. But whatever, I just want the damn thing to work lol.

You should find a strip down on this site for this gearbox .