Jeff_Keryk

What is the cause of chewed up distributor tach drive cross gear? The distributor is installed correctly; the cable is not bent. I replaced the cross gear not so many miles ago.

...Roger...

Sometimes the gear eats into the back of the housing.
Sometimes if the brass coupler is worn it will allow the gear to ride away from the mainshaft gear.

robert.sperry

The likely cause of the damage on the cross shaft is damage on the mating gear teeth on the main shaft of the distributor. If you put in a new cross shaft and it is being driven by damaged teeth on the main shaft then the cross shaft will get chewed up again. You will need to pull the distributor, disassemble, and replace the main shaft. There may also be wear in the area where the cross shaft pilots in the distributor which will also need to be repaired. Also if you have been running the engine for a while with damaged teeth, the bits of metal inside the distributor may have damaged the lower bearing for the main shaft and this bearing will also need to be replaced. In short a complete rebuild of the distributor is likely required.

Paul L

Robert,
That is exactly what happens. In this case it was the later-model brass button that disintegrated. Note the scoring on the bearing and shaft.

redvetracr

later model GM tach drive distributors came with a plastic button, bubba put your brass one in.

Paul L

You are labelling most vendors as Bubba as they advertise the bronze (not brass as I stated) button on their web sites. That is not fair.

The kind folks at ZIP re-did the distributor above completely with new components for which I thanked them in an earlier thread. Their button is nylon for $2.00. Others offer bronze for 1968-74. So I do not believe Bubba is part of this thread. Your choice as to which button is the right choice? I went with a departed Forum colleague on this one (L**S).

The distributor in my 1974 at the moment is from 1967. No buttons but carefully lubed. Rebuilt by me. It works well. The re-built ZIP unit is in reserve.

Jeff_Keryk

My late brother rebuilt the distributor for me. As I recall, we replaced the main shaft, though I am not 100% sure as this was years ago. We did not replace the bearings (bushings?). I might ask our friend if he will do a rebuild for me. Your help and thoughts are appreciated. I love these old cars.

morganjd

So what is better button to use? Bronze? Nylon or set screw?

redvetracr

what did the factory use a nylon button, bronze one or a set screw? If your housing is worn (and it`s a housing worth repairing) I would have a machine shop mill the worn spot and place a piece of steel in there ala Lars. he did a 65-67 BB housing for me, it wasn`t real cheap but with Lars you get what you pay for...

TNX ZORA

When our original gear stripped out all I did was clean the housing, install a new gear, and most importantly, install a Zerk grease fitting. That was many tens of thousands of miles ago. I don't remember getting involved with any special button.