<VV> Differential setup

tkalp at cox.net tkalp at cox.net
Fri Jan 5 10:21:37 EST 2018

Mike Dawson put together at two page tech sheet on Corvair differential overhaul and adjustment that should be a help.  With the new gears you may have to reset the pinion depth.  Mike's notes provide a good starting point for the shim.  Without special tools the only way to check for proper pinion depth will be to put everything together adjust the pre-loads and backlash then check the pattern.  Here is the section of Mike's tech sheet that applies to what you will need to do:
Inch Pound Torque Wrench (Beam Type) and Fabricated Tool For Pre-Loading Bearings:
I welded a nut on the end of a donor 4-speed main shaft to assist in determining the
proper bearing preload on manual differentials and I welded a bolt and shock washer on
to a donor governor drive gear for checking automatic differentials. Differential cases
expand with heat and all four bearings will loosen in service, so applying the proper
preload is critical for the life of the differential. After years of reading manuals over
and over while setting up differentials, I have come to the conclusion that 6-8 inch
pounds preload on the side bearings and 6-8 inch pounds on the pinion bearings works
just fine. First establish a .010 lash as a starting point, load the side bearings to 6-8 (with
the pinion bearings at zero) and then add 6-8 more to the pinion bearings for a total of 12-
16 inch pounds.
Ring and Pinion Contact Pattern: This is equal in importance next to the bearing preload
and very critical for wear/noise. The Corvair shop manual has so many errors in it
that you must read carefully and recognize that the pictures of patterns in the manual are
from other Chevrolet differentials (they are backwards) and are quite confusing. They
also refer to contact patterns on the pinion gear which is in error. If you are starting from
scratch in your shimming, use a .015 shim as a starting point and change only in .003
increments. You can change patterns both with shims and with lash adjustments, so take
the time to practice. A tube of Prussian Blue (Permatex) marking paste and a small brush
are my favorites for checking patterns.
Ring and Pinion Lash: This is the least critical of the adjustments but to determine what
the lash is you will need a dial indicator and the hardware to use it. If your bearing
preload is correct and you have achieved a good contact pattern after starting with .010,
any reasonable lash above .003 I think would be acceptable. Again the critical items are
preload and pattern.

The full document and over 100 other tech tips are available for download on the HACOA (Heart of America Corvair Association) web site.

T. Kalp
Wichita, KS

---- Otb Customs via VirtualVairs <virtualvairs at corvair.org> wrote: 
> Any tips or advice on aligning / setting the differential before matong it
> back with the transmission, the differential manual is a little lacking on
> the install process but thorough on the breakdown process. It is a 62 rear
> end with automatic trans I don't think it has positrac, we have the new
> gears installed and are not sure about the shims and what all needs done
> before setting the lock tabs
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