I've just found the noise in my gearbox. Pulled it out a couple of weeks ago, wasn't that fun. If anyone has an easy way of getting a gearbox out of a vette please tell me, but I digress.

The symptom was that the box appeared to have excessive back lash and a clicking noise in the lower gears when backing off. Pulled the mainshaft and checked all bearings and every thing looks good, no wear and all is nice and tight. Pulled the countershaft and gear cluster and found the problem. All the needle bearings are good and so is the counter shaft. There is a plate, cut to the same profile as the front gear that is rivetted to the cluster. It appears to be an oil scavenger or pump for the front main bearing on the mainshaft. The problem is two of the three rivets have been ground away allowing this plate to rub on the gear case. Every time one of the rivets goes past the oil hole it clicks. Does anyone know where I can get replacement rivets or if this plate is essential.

I'm a transmission builder,(30+yrs)and I believe the piece you are asking about is basically a "tensioner" to keep the backlash on the cluster to an almost acceptable noise level. M-20 gearboxes have some normal gear "rattle",especially in rev. or just at idle in neutral. They are not as noisy as the M-21, but a little rattle/growl is OK. I would just remove the thing and make sure the front of the cluster is flat in the area where the rivets were, and put the trans back together. If you must have the thing "correct", the only option is to replace the cluster, and there's no guarantee the new one will have that piece.

thanks for that and I was hoping that I could just do without it. I'm presuming I will need to endure I have the correct thickness thrust washer at the front of the cluster to make up for the missing plate?

I'm not sure that piece has anything to do with the end play on the counter-shaft. If it is the piece I'm thinking of, the thrust washer for the counter actually fits inside of it, not on top of it. You shouldn't have any clearance problems assosiated with removeing the plate. Just check the end clearance and make sure it's got some, but not a lot.(How's that for a scientific explaination? !!!)You just don't want too much , or it to be too tight. You should be able to barely move the shaft fwd. or back. Good luck and if you run into a problem I'll do my best to help.
ps...nice car !!!!

I've pulled the plate and had another look at the gear cluster. The thrust bearing needs to stay original as the plate has nothing to do with endplay. Talked with Muncie and the later model M20s didn't have theses plates.

Sounds like a winner to me!!! Have fun!!