<VV> 65 Posi Differential Numbers, durability

[NicolCS@aol.com]

Paul, identifying a posi with numbers is very difficult, given all the  grime 
but the 65 3.27 code is AC and the 3.55 code is AD.  The codes are  very 
lightly stamped near the interface with the transmission on the right  side.  The 
area must be very clean and the light exactly right in order to  read them.

A much better way is to ID them physically.  65 cases are unique:  4-bolt 
transmission mounting with lower mounting areas cast and machined for the  lower 
control arms.  Posi ID: grab the two output yokes and rotate  one.  If the o
ther one rotates with it as-if they were locked together,  that's a posi.  If 
the other one does not rotate or rotates opposite,  that's an open (non-posi).
 
In the event that you find a '65 posi, you can count gear teeth to  determine 
the ratio or count turns.
 
In a related post, someone asked about posi durability.  I have had  good 
luck with stock posi units however I have repaired quite a few that cracked  
their side covers (an internal piece). When the posi is asked to "do it's  thing", 
tremendous internal forces are applied to the side cover - some of the  
original pieces were apparently better than others.  There's now a  beefed-up 
version available that is stronger than the original parts.  I  have three posi 
differentials, all built with original parts that survived their  original use 
and they have served me well.
Craig (been there) Nicol


I'm looking for numbers or codes to determine what would be  positraction unit
for a 1965 Corvair 4 speed. A guy has many Corvair units  from years ago and 
he
cannot remember how to tell them apart. I want to buy  one from him and don't
want to make a mistake. Also ...where do you look for  the number? Thanks.


Paul Drake