M21 Leaky countershaft

[joe gushen]

I just Pulled the M21 out of my 66 roadster because of it leaking from the front of the Transmission. The leak is coming for the counter shaft! How do you fix that? The transmission was rebuilt so what did the guy not do or was supposed to do?

[Howard Nardick]

Re: M21 Leaky countershaft

you need the case machined for a bushing, and of course a bushing installed.....HN

[Joe L.]

Re: M21 Leaky countershaft

joe-----

There are 3 reasons for front-of-transmission leaks on a Muncie:

1) worn/distorted countershaft bore. The best way to fix this is to have the transmission case bushed by someone that knows what they're doing. However, the transmission needs to be completely disassembled to do this.

The other way to do it is to scrupulously clean and degrease the countershaft end and adjoining area of the case. Then, apply silicone sealer to the interface area between the countershaft and the case. I would use ONLY Permatex Ultra Copper for this. This might work and it might not. It's worth a shot, though, before proceeding to more difficult repairs;

2) worn threads for the bolts that retain the front bearing retainer to the case. The best way to repair this is to install "Thread-Serts" using Permatex Sleeve Locking compound (green) as the sealing agent. Then, install new bolts with Permatex Pipe Thread Sealer with Teflon.

The next best way is to just apply a generous amount of a non-hardening sealer to ULTRA CLEAN bolts and threaded holes. Depending on the degree of wear, an anaerobic thread locking compound like Lock-Tite 242 (blue) might be all you need to seal the bolts. Either way, the bolts and threads MUST BE ULTRA CLEAN if this method has any hope of working;

3) damaged gasket between the front bearing retainer and case. This should always be replaced with a NEW gasket. I use just a very thin film of Permatex Ultra Copper on both sides of the gasket.

[Phil P.]

Re: M21 Leaky countershaft

if you rebush the cluster shaft have it off set towards the main shaft .006 this will off set the high torque "spread" from a hi-po motor--good luck