<VV> BG Services for Corvair powerglide transmissions

[Brent Covey]

Hi Randy,

> Have any of you used the shops advertising the BG Services method of
cleaning
> out and replacing all transmission fluid including that in the torque
> converter.  Could this method work on our Powerglide transmissions?

As has been pointed out, you would need a transmission that had cooler lines
like the Greenbriers have to use this service. Keep in mind the torque
converter is sort of a centrifugal debris collector, and any real
contamination in the transmission that makes it in there is going to stay
there forever, so in any case when you feel the transmission has been
seriously contaminated (like submerged in a flood) the converter really
should be replaced or rebuilt.

Normally the fluid in a Powerglide will not need replacement for the life of
the car, Corvair Powerglide is a very cool running transmission and the
fluid doesnt degrade much over time. If you were pushing a Corvair hard
enough to be hard on the transmission you'd be going thru engines fast, the
trans is harder to overheat than the engine by quite a long shot. In 25
years I havent encountered an overheated seal in a Corvair Powerglide; on a
regular GM car theres often heat damage.

Corvair torque converters seem to have very weak stator clutch sprags and
lose thier torque multiplication abilities sometimes to varying degrees- the
usual tipoff is poor traffic performance degrading into glacial standing
start acceleration eventually. ANY Corvair Powerglide should feel enough
'snap' to throw loose gravel or spin the tires on grass at the very least, a
110HP should be able to spin stock sized tires from a standing start on a
wet road pretty easily at low altitude. If a particular car seems slower
below 20 mph than similar cars in a given area converters are usually a good
place to start looking if tuning seems OK etc.

One failure I have also encountered is failure of the rivets holding the
driven turbine to its hub, the car will lose drive in every range when these
parts seperate, literally instantly. I have never noticed any warning signs
this was about to occur, there doesnt seem to be a death rattle or anything,
the car just quit. It can be diagnosed by testing pressures with the engine
idling running thru the drive ranges.

Heres are some good Corvair Powerglide parts illustrations including the
converter disassembled;

http://charlietranny.com/CorvairPGparts.htm

Just the converter;

http://charlietranny.com/CorvairPG-A.JPG

Most metro areas have a converter rebuilding shop. I am leery of them
because parts for internals are scarce and the balance and ring gear are
critical, but the old time places might be OK. I am not sure what the
vendors offer for converters currently but that may be a safer source for
one if a person needs one.A fresh converter is a worthwhile addition to most
Corvairs after 50,000 miles if you are working in there anyhow. I also feel
its a good practice to replace the bushing in the hub and the seal on the
back of the differential case for the converter any time the transaxle is
disturbed, the seals often leak if they are reused.

If you want to change the fluid as completely as possible, let the car stand
overnight before you drain it, and you'll get all the stuff in the pan and
about half whats in the converter after it leaks down. The first time you
probably should take the pan off and clean the screen, subsequent occasions
loosening the filler tube nut should be ok, much of the debris in the
transmission will date back to the factory parts breaking in when it was
new.

Corvair type A transmission fluid current replacement is Dexron III. Type A
was essentially 20W with some anti foaming and other additives-

One last thing, when a Corvair has been standing a very long time, all the
debris in the converter settles to the bottom of it. When you get the car
started run it for a minute or two and then shut it off a couple times to
allow the garbage to be redistributed evenly. It would not surprise me to
find up to an ounce of material in a converter and thats a considerable
imbalance if its all sitting in one spot.

Hope thats some help,
Brent Covey
Vancouver BC