M20 Trans Rebuild Noise - Break In Needed?

[Jace H.]

Hi All,

I bought a correct 1967 dated rebuilt M20 4-speed transmission from Ron Worthen in California recently to install in my 67 roadster as I was rebuilding everything from the ground up and did not have a correct trans in my car. I have everything back in the car and everything is working flawlessly except for some whining noise when the car is in nuetral, when shifting and accelerating from 1-4 gears. Motor and trans only have 30 miles on them since rebuild. It is not the clutch or throw out bearing. Noise is still there at 40 mph in gear with motor off. Ron says that it is due to the trans having been re-bushed and that all gears and components are tight and need to loosen up. Anyone else experienced this? How many miles is reasonable to expect to loosen up the gears and stop the noise? I REALLY don't want to take the trans out and ship it back to California. Has anyone else dealt with Ron? Any input is REALLY appreciated.

Thanks,
Jace Holt

[Joe L.]

Re: M20 Trans Rebuild Noise - Break In Needed?

Jace-----

Some noise is normal, ESPECIALLY if any gears were replaced in the transmission when it was rebuilt. Whether or not GM NOS gears were used, you will have a situation of a new gear "wearing into" a used gear. All of the noise may not disappear, either. That's just how it is with a rebuilt transmission if gears are replaced and mated with other gears which are used. The only way around it is to replace ALL of the gears. That gets VERY expensive, especially if all NOS gears are used.

I think that the transmission will quiet down as it wears in, but some noise will likley remain. Keep in mind that even a NEW Muncie trnasmission was not absolutely quiet and whine free.

[Joe C.]

Re: M20 Trans Rebuild Noise - Break In Needed?

Jace:

When the trans is in neutral, and the clutch is let out (engaged),the input shaft which is integral with the beveled gear driving the countershaft(aka "pin", "cluster shaft"), are all turning at engine speed. When you select a gear and let out the clutch, then the rear half of the input shaft, is engaged and transmits engine power to the output shaft. Actually, the input shaft + output shaft = mainshaft.

In any event, no matter what gear you are in, including neutral, and the clutch is let out, then the forward part of the mainshaft, and the cluster, is turning. If the mesh between the drive gear on the input spline, and the driven gear on the cluster is improper, then the trans will whine all the time, whenever the clutch is let out. If the cluster shaft was not bushed properly, and aligned properly, then that is likely the cause of the whine.

Some of the terminology I have just used may not be exact, but hope you get the idea.

Joe

[Jace H.]

Re: M20 Trans Rebuild Noise - Break In Needed?

Thanks Joe,

I put 30 miles on the car today and the noise has diminished some. Especially in neutral. Is this a good sign?

Jace