<VV> Overdrive Transmissions

[Jim Becker]

If I ignore all the engine discussion, I THINK the original question 
essentially was whether you could change fourth gear of a Corvair 
transmission into an overdrive.  The simple answer to that question is no. 
Fourth is direct drive, yielding a 1:1 ratio by coupling the input and 
output to each other.  You can add, change, remove gears all day and all it 
can possibly change is everything but fourth.

There are other options.  However, since the countershaft gears all come 
together in one piece, any ratio changes will start to get complicated (read 
as $$$).  To get an overdrive, you could change another gear to run faster 
than 1:1.  The obvious change would be to make current first into overdrive. 
There are complications.  Your shift pattern would change.  Going 
sequentially through the gears would mean going though the current positions 
2-3-4-1.  Using an FC transmission might yield some better ratios for 2 and 
3 (the new 1 and 2).  There are some complications.  Using the early 
transmission, you would end up with a non-synchro overdrive.  No matter 
which transmission you use, you may not be able to make clearance in the 
case for the extra-large gear on the countershaft.  Messing with first gear 
ratios will foul up reverse.  It may be easier to change second or third, 
which avoids both the non-synchro and reverse problems.  The synchronizer 
parts may limit how small you can go on the driven gear.  Also, it would 
make for an even stranger shift pattern.

Overall, you would probably be better off to use an FC transmission and find 
some 3.08 final drive gears or have a custom ring and pinion made (if you 
could even find someone to do it).

Jim Becker

-----Original Message----- 
From: DickR13607--- via VirtualVairs
Sent: Friday, October 30, 2015 9:37 AM
To: virtualvairs at corvair.org
Subject:  Overdrive Transmissions


I understand the rpm problem, but, as an engineer whom worked for  FoMCo
for a number of years, I was taught that lower rpm's meant better  gas
mileage and longer engine life.  Also, why have various people spent  years
working on possible 5-speed transmissions for Corvairs?  I thought my  idea 
was
much less costly.  Would it work?  I don't know, but I  haven't seen 
anything
that addresses that question.

Richard Royle
66 Corsa Turbo

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