<VV> Other Vehicles With The Same Gear Lube Requirements

[eamsquared at comcast.net]

I've been following this thread from the beginning and can convey some important information on this subject.  I am the original owner of my '66 Corvair 110 PG and also the original owner of my 1972 Corvette with an Muncie M21 4 speed.  I have been a member of CORSA since 1969  a member of NCRS since 1985.  Interestingly enough the Spring Issue of the NCRS magazine also has an article titled "Navigating Gear Oil Choices for the Muncie Transmission".  My Corvair Owner's Manual specifies MIL-L-2105B for 3 & 4 Speed transmissions.  The NCRS article states that the C2 owners manual for Corvettes also specifies 80/90 MIL-L-2105B gear lube for the M21 trans.  Obviously GM specified the same gear lubricant for mid '60's Muncie transmissions. 
  
The interesting point is that both the Owner's Manual and Shop Manual for my '72 Corvette Muncie M21 4 speed specify SAE 80 or SAE 90 GL-5 gear lubricant.  I don't believe there are any significant design differences between the Corvette M21 in 1972 and C2 Muncie M21 transmissions. Since both the Corvair and Corvette Owner's Manuals specified the same standard transmission gear lubricant back in the sixties, I would think the GL-5 gear lubricant would also be suitable for Corvair transaxles and transmissions. 
  
I am not making a recommendation here but only pointing out the fact that GM recommends GL-5 gear lubricant for my 1972 M21 whereas GM recommended MIL-L-2105B gear lube for the Corvette M21 in the mid sixties which was the same spec used on standard transmission Corvairs in the mid sixties.  Take it for what it's worth. 
  
Erich Meyer 
Bayshore Corvair