<VV> manual transmisison oil

[NicolCS@aol.com]

In a message dated 3/20/2004 6:21:35 AM Pacific Standard Time, 
virtualvairs-request@corvair.org writes:

<snip>
> I distinctly recall that the automatic transmission AND the (integrated)
> differential in my 1992 Plymouth Voyager ran on ATF. Now, this does NOT
> satisfy me that the Corvair differential would be happy running with ATF,
> but it DOES raise the question in my mind: what's the difference between
> differentials that ARE happy with ATF and those (like the Corvair's) that
> are not? Anyone know?
<unsnip>

I'll begin by stating that I am not a lubrication or driveline engineer, just 
an amateur tinkerer.  Having said that...  Many / most FWD differentials have 
spur gear final drives, similar to transmission gear designs, only larger.  
Cars with North/South engines have to have a 90 degree turn in the driveline, 
so they use hypoid final drive gears.  In my understanding, the sliding contact 
of the hypoid gears is the reason for the EP (extreme pressure) requirement 
in Corvair and other conventional differentials.
Craig (open to education here) Nicol