M-20 fluid capacity

[Donald O.]

How much gear lube should a M-20 take for a fill
I am using Sta Lube GL-4, 80-90w.

Don

[Richard G.]

Re: M-20 fluid capacity

According to the 1965 Chassis Service manual The four speed takes 2.5 pints.

[Donald O.]

Re: M-20 fluid capacity

Just having a hard time finding a non GL5 lube. All I've found is a GL4/GL5 in 80-90w and 85-90w and a GL3 in 80-90w.
The GL5 rated has a much higher level of sulfur which our synchros do not like.

IF I can find a GL4 in 85-90w would that be good to go?

[Duke W.]

Re: M-20 fluid capacity

The original spec was Mil-L-2105D. Look at your owner's and service manuals. This mil-spec was cancelled long ago and replaced with API 80W-90 GL-5, and I think sometime in the seventies the new service manuals began listing 80W-90 GL-5, which should be readily available from any auto parts store.

Brand is not important. Just make sure the package has the API "donut" with 80W-90 GL-5.

Forget the "yellow metal corrosion" myth. I have never seen and old manual transmission that showed any corrosion - only normal wear from long service. Nor has anyone I know of ever reported "corrosion", and this includes guys who have overhauled dozens of old manual transmissions.

Duke