[DeTomaso] Steering rack adventures/ oil specs
JDeRyke at aol.com
JDeRyke at aol.com
Tue Aug 5 18:03:35 EDT 2008
In a message dated 8/4/08 6:11:11 PM, adin at frontier.net writes:
> What do we think of the new trend (ok, not so new) of specifying water thin
> oil in transmissions?
>
> Do we know more than the engineers? If one were to use "better" (my term)
> lubricant, will it void the warranty?
>
Not a matter of knowing more; this was strictly a bean-counter move. In 1982,
GM started adding ATF, a hydraulic oil with no load-carrying additives, to 4
speed trannys. The zero-wt oil dropped the internal drag enough to raise GMs
CAFE (corporate average fuel mileage) rating. And the few performance owners
that fragged their trannys and differentials were cheerfully warranty-replaced
but didn't significantly affect The General's bottom line. I bought one of
these with 12,000 lightly miles on it and 6 months later seized the tranny in
2nd gear at an autocross. I drove across town with the gearstick in Neutral and
on teardown, it took a torch and every bit of my 12-ton press to break the
normally-rotating 2nd gear free of the mainshaft.
I used to have phone numbers at some of the Detroit factories, so I called
and asked what the idea was of running ATF in a std trans. The engineer that
answered the phone at the Powertrain Division tried to tell me they're redone the
internal clearances and metallurgy for ATF. As it turned out, the Z-28 trans
was a Saginaw 4-speed; when I told him I'd mic-ed everything, found no
differences so I repaired it with NOS gears from a 1966 Corvair Saginaw with
"non-upgraded' gears and 90-wt gear lube, and it ran just fine except cooler, there
was no answer. The next time I tried calling (when the differential went out
at 26,000 miles- 1 K out of warranty), the phone number had been changed.... At
least three Nor-Cal Corvette owners also lost trannys and one diff until the
news of the wrong lube got around.
FWIW, I have now lost three (3.0) Chev posi differentials- 2 in brand new
cars and one in the low mileage '82 Z-28. I am now convinced that GM cannot set
up a posi differential; and the next new car I buy will NOT be a GM.
As far as warranty goes, do you really want the thing fixed exactly like the
one that broke? On the latest- Judy's '97 Z-28, I didn't even bother with the
warranty. I took it to a performance shop to fix it right for $1000. The shop
owner said they saw an awful lot of this stuff. FWIW- J DeRyke
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