<VV> Tranny and rear axle oil

BobHelt at aol.com BobHelt at aol.com
Wed Apr 1 21:22:05 EDT 2015


With apologies to Smitty, please let me correct a few ideas and add some  
comments.
 
First, we normally think of grease as solidified lubricant--at least  
partially solidified as in mushy. That is not what one should put in a  
transmission or differential. We want to use a gear lube for these gear boxes.  Gear 
lubes are quite fluid, even at freezing temperatures. No grease  please.
 
Next, whoever wrote the top paragraph likely did use a good lube, as far as 
 he described it anyhow. I'll bet that the lube used had nothing to do with 
the  leaks. He should check his work of replacing the gaskets and seals. 
That would  seem to be the likely problem area. As stated many times here, 
80-90 weight GL-4  is what he should be using. At least something in the 80-90 
range depending on  the climate where he lives. But definitely GL-4.but no 
GL-4/GL-5
 
OK, let's talk about gear lubes. First GL-4 and GL-5 are the only ones  
currently being marketed.   There are no GL3's or GL6's any  more!!!!!  And 
Smitty, The lube industry still does care about our poor old  Corvairs. That is 
what GL-4 is for. And why it is still available. GL-4 has been  on the 
market for ages and is a direct decendent of MIL Spec
L-2105B specified in the Shop Manuals. The latest Mil Spec  is L2105C  is 
identical to GL-4. So here we have a Mil Spec backing up  what which lube 
should be used for Corvairs. How can you go wrong? You can't.  Gl-4 is exactly 
what the Corvair needs. It provides the Hi Po dif gears and also  the 
4-speed brass synchro blocker rings all the protection they need.
 
Then there is GL-5 gear lube. This lube is specifically designed fo,r and  
sold for, non- brass synchro blocker rings. Thus it contains NO anti 
corrosion  additives to protect these rings. Why? Well because most modern manual  
transmissions do not use these brass rings. Thus, no brass......no 
protection  needed. And MT-1 isn't for Corvairs either.
 
But as Richard1 has pointed out there is another concern about using GL-5  
in our Corvairs. Here is why. In the Corvair 4-speed trannys, when a gear is 
 being selected the shift is made only after the two moving (rotating) 
parts are  at the same speed. The brass blocker rings cut-thru the lube to make 
direct  contact with the gear shaft on the tapered raised portion by 
friction so  that the gear shaft is brought up to correct rotational speed. The 
GL-4 lube has  the correct viscosity and characteristics to allow that to 
happen with  minimum effort and wear. 
 
But GL-5 has increased slipperiness and a Corvair transmission using GL-5  
would require greater force to implement the shift just described. This 
greater  force would increase the wear on the brass synchros and greatly shorten 
their  life. 
Thus GL-5 is not recommended for MT Corvairs.
 
I hope that this clarifies the situation.
 
Bob Helt
 
 
In a message dated 4/1/2015 5:00:03 P.M. US Mountain Standard Time,  
virtualvairs at corvair.org writes:

I had a  shift seal leaking in my 62 Rampside I drained all  the grease out 
 
and replaced the seal and put 70/90 grease back in.  From everything  I'm 
reading I did a No NO. Should I drain grease out and replace with  
something 
else, or should I add a additive.  I've only put about 20  miles on truck 
since I change it.  Thanks want to do the right  thing
-------------------------------------------------
Smitty  Says;  You and me both buddy.  The more I learn the more I am  
confused about what is right.  I have written several hundred words  and 
written a thousand trying to get a definitive answer and so far I know  
very 
little.  If you used GL-4 it will work for you a long time  before it does 
any damage.  If you used GL--5 I would get it the heck  out of there.  It 
will do very little of what you need.  I am  sure you will get quite a bit 
of 
advise on what to use.  I would  strongly suggest you go on the net using 
key 
words "The difference in GL  -4 and GL-5 gear oil",  and see what you can 
learn.  Even then  you have to be leary of some company claims such as 
AMSOIL.  It may  be the greatest lubricant in the history of mankind but I 
have met all  their claims over the years using Dinosaur oil.  Subjected it 
to  excessive heat and ran excessive miles between changes.  In my million  
miles of driving so far I have never had a engine or transaxle failure I  
could blame on  "Poor oil".  We are stuck with trying to get our  transaxle 
lube to do two things.  It has to be an extreme pressure  lube for the diff 
and it has to have chemical protection for our  Synchros.  It appear to me 
that either that is a difficult  requirement to meet,   OR   the oil 
companies expect  to sell so little to us Corvair owners that they simply 
don't give a damn  if they do or not.  What ever else you do don't use any 
of 
the modern  front wheel drive lubes that are thin like water, no matter how 
many times  it says 70, 80 WT.
Read all you can on the subject and make the most  infirmed decision you 
can.  




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