<VV> Corvair Powerglide

Tony Underwood tony.underwood at cox.net
Tue Oct 27 02:17:24 EDT 2009

OK, I have a PG question:

I've worked on so few Powerglides as to be ignorant of just about 
everything in them because I never had one ever break on me.    The 
1960 4-door still has its original unmolested 200k+ miles PG.

Over the weekend I fixed its vacuum plumbing so as to smooth the 
shifts out (mud daubers had stopped up the line to the vac. mod. 
valve a couple years earlier when I had the engine out) and took it 
out running today, enjoying shifts that didn't go THUMP.    It had 
been like that for some time, no vac. mod. function until I finally 
got around to fixing the hoses etc.


I took the car across town, parked, then went back out and fired it 
up to go back home and backed out of the spot, popped it into drive, 
smoothly engaged, and I gassed it...   transmission whined and the 
engine flared up and the car barely moved.   Off the gas immediately, 
didn't wanna burn up the lining which can happen quick if it slipped 
like that.     Shut off, checked for ATF leaks, started up and 
checked fluid level, ok.

Back in gear, SLOWLY moved forward, no slipping.   Gassed it a bit, 
whine and slip.   In reverse, NO whine or slipping even when lugged 
hard.   Got it onto the streets, slowly up to speed, shifted sloppy, 
engine rpm flared and mushed into gear but once in Drive it wouldn't 
slip, drove normally.

Got to my side of town, and it wouldn't climb the hill to the 
house.    >:-o    I was afraid I'd burn up the lining if it slipped 
much so I backed down and stuck it in a parking lot at the bottom of 
the hill... and crawled around looking for hints.

I pulled the vacuum hose off the line to the modulator valve just for 
the heluvit and tried it again.     Back to normal, albeit with hard 
shifts... but NO slipping anywhere.    Up the hill it went, no issues 
at all.

So:  PG gurus...  am I on the last legs here?   Or has the vacuum 
modulator valve gone wacko (doesn't seem very likely)?   And why 
slipping in Low and not Rev.?   Servo piston/valve?  Is a band 
adjustment likely to help here?    As mentioned, I never had to fix 
one so Powerglides are foreign territory for me other than what I've 
seen in manuals.    The transmission is quiet and smooth and fluid is 
pink.  To my knowledge it has never had as much as a screw turned on 
it since it went into the car at Willow Run.   I've owned the car 
over 25 years now and this is the first transmission issue to come up.

Without that vacuum line attached, it works like it always 
has.   Attach the line, it's damned near unusable.    I wouldn't have 
thought it would make that much difference.

I welcome any input here... and I guess it's possibly time to dig up 
a PG service manual.

tony..   (I do have another PG with 30,000 original miles on it if 
need be but wanna keep this one, jus' b'cuz)   

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