[FC] differential question

[Ken Hand]

Depending on what engine you have should determine what diff gear ratio you want to use. I know of several FC's with 3.27 gears. With that and using a 164 cu in engine I prefer the 3.55 gears.
I would not use a 1960 differential. There are a few hard to get parts and I will explain later another situation.
The 61-64 differentials are internally all the same, the 65-69 differentials are all the same internally. Can you just take a 65-69 diff and install it without modifying it? NO.


Depending on how you are going to drive the FC will determine my recommendation. If you are going to drive it just on the road like an automobile with no racing instincts intended then any diff will work just fine. If you intend on autocrossing or performance driving you might want to think about using the 65-69 internals but they need to be modified. The reason for that is the 60-64 diffs have 6 ring gear bolts and the 65-69 ring gears use 9 bolts. So unless you are going to hammer on your FC hard it is not worth the extra to modify the 65-69 internals. There are inherent weak spots that are common to all Corvair differentials that would need to be addressed like the racers do if you drive hard.


If you look at the wear patterns of the drive yokes in the differential the passenger side, short yoke, will have more play or wear than the driver's side, long yoke, will have less. 


I am not going to rewrite the book as all of this stuff is talked about. 


If you have questions I will be glad to answer to the best of my ability by talking about it.


Ken Hand
Handy Car Care
248-613-8586
www.corvairmechanic.com

For those that have fought for it, Freedom has a flavor the protected will never know.




-----Original Message-----
From: Phil via Corvanatics <corvanatics at corvair.org>
To: corvanatics <corvanatics at corvair.org>
Sent: Wed, Apr 4, 2018 5:05 pm
Subject: [FC] differential question

have a question about differentials,maybe someone can help,iam going to put in 355 gears,what diff is better to use,1960 diff  1961-1964 diff 0r 1965-1969,and why should I use it,i know the 60 diff has two short yokes,and the others have one short and one long,can someone tell me why the 60 is the only one with two short yokes,and why did thay change to one long,thanks for info...
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