<VV> Some interesting facts on Gear Lube

BobHelt at aol.com BobHelt at aol.com
Tue Apr 7 11:42:25 EDT 2015


I know that this subject is getting quite boring for some of us, but I have 
 discovered some facts not presented here before and feel the need to 
summarize  the Gear lube uses in Corvair automobiles.
 
So here goes~!!!!!
 
GL-4, GL-5 and MT-1 are the only active Gear lube designations.
MT-1 is for non synchro transmissions so it is NOT for Corvairs
 
Despite some other differences between GL-4 and GL-5, the important  
difference for Corvair 4-spd trannys is the greater slipperyness of GL-5 that  
tends to add wear to the synchros if used in our transmissions. Tarnishing of  
the brass rings is a non issue since both have protection. Both can be used 
in  our differentials.
 
Despite the fact that GL-4 is currently being marketed, the GL-4  
designation was inactivated in 2010 according to internet sources, since the  test 
procedures and equipment are obsolete.
 
Because of these obsolete equip and procedures for verifying GL-4 by  
testing, the industry has agreed to produce GL-4 lube, not the old way but  by a 
new way. GL-4 is currently being manufactured by adding a quantity of  
one-half of the GL-5 additives to the base oil. So GL-4 now is similar to  
previous GL-4 oil but not identical.
 
I was unable to determine exactly just when the GL-X way of rating gear  
oils went into effect, but it must have been around 1975, long after the 
Corvair  ceased production.
Thus, the Corvair requirement of gear oil meeting  Mil-L-2105B later  
turned into GL-4 (in about 1975). Corvairs  NEVER required the GL-5  equivalent 
so Redline is definitely wrong about this.  And thus I question  Red Line's 
knowledge of GL-5 applications. 
 
Red Line says their gear oil meets GL-4 but then goes on to say that it is  
not for hypoid gears. This a conflict in fact and cannot be true since GL-4 
 allows use with hypoid gears. Either it meets GL-4 and can be used in 
hypoids or  it doesn't meet GL-4 for hypoid use. 
Another case of Red Line's questionable information.
 
Bob Helt


More information about the VirtualVairs mailing list