<VV> What ATF?

[Jim Davis]

Although I have been repairing Corvairs for 51 years, I bough my first 
PowerGlide car in 1996.  It was a 1966 Monza with the 140 engine and 
A/C.  I rebuilt the PG and never had a problem.  In 1999, I bought an 
UltraVan, 110 engine and PG.  I changed to a 140 166 cuin engine with a 
140 PowerGlide (with ATI HD clutches) in 2004 and noticed the low band 
would slip if I applied more than 3/4 throttle from a full stop.  I 
tired adjusting the TV rod so that the secondaries would be barely open 
when the TV valve was in the kick-down detent, as well as turning up the 
idle pressure to 58 psi.  I was running Dexron-5 at the time.  Not much 
help.  I just learned to ease off from a stop. There was a considerable 
surge from low to drive and light throttle when the trans fluid was over 
210 F; although it shifted fine at moderate throttle.  I thought the low 
band might have hardened from over temps by previously owner, so I 
installed a new Clark's rebuilt low band - no help.  Finally I bought a 
NOS front pump from Clark's and installed it with no help.   Finally I 
changed the 140 valve body from the car to the UltraVan.  Again no help. 
   In the UltraVan, I change the engine oil, drop the PG pan and blow 
all the oil out of the torque convertor using Bob Ballew's technique and 
change the gear oil in the diff every spring.

  I went back to Dexron-3 in 2005 and it helped greatly, but I was 
worried about the trans temperatures.  Out west, climbing the Rockies  I 
often spend 30 to 40 minutes at full throttle in low range at 4,000 to 
4,500 rpm getting the 5,400 lb coach up the mountains.  250 F is not an 
uncommon trans fluid temp (measured in the oil cooler line going to the 
B & M Hi-Tec oil cooler by a good Intellitronix digital gauge) in the 
mountains in July.

I built as 190.5 cuin engine in 2007 using Ray Sedman's AP-500 cam; 
Michael Leveque did the work on the heads.  That moved my max torque 
into the 180 ftlbs range.  I talked to Mike Dawson at one of the Wichita 
Tunas, and he recommended I try Dexron-6 with 10 oz of Trans-X.  It 
worked as adverticed.  No slipping or shuttering of any sort.  I can now 
floor the throttle from a standing start with out fear of low band 
slip.  Shifts are immediate at 4,900 rpm, almost jerky, at full throttle 
entering the Interstate. All this is imperical info; just what worked 
for me - your results may vary.

Jim Davis

On 4/8/2015 4:27 PM, Joel McGregor via VirtualVairs wrote:
> As someone that rebuilt transmissions for years and knows a guy that used to write manuals & do research for ATRA - I use Dex VI in everything  (friend agrees).  I've never seen a fluid that would make a transmission slip.  The different properties would make the shift feel different if it wasn't designed for that particular oil but that's it.  B&M used to recommend type F for everything.
> I use VI in everything from TH250s to my wife's Saturn.  All of my running Corvairs have manual transmissions so I haven't run it in a Corvair yet but I will if I ever drive an auto.
> I also change it every 3000 miles.  That's much less trouble than rebuilding the transmission.
>
> Joel McGregor