[DeTomaso] Steering rack adventures/ oil specs and tranny oil
Peter Kovacs
peter-kovacs at sbcglobal.net
Wed Aug 6 01:46:49 EDT 2008
Similar to the Ford T-5s and WC T-5s running ATF. Normal use they worked fine. After a long run on the freeway at an inappropriate speed. I pulled over to put the top up and crunch, crunch crunch with every shift. Evidently the "no load" capability and the inability to cope with the heat generated from the overdrive fifth gear, cooked the bearings. I was told having Redline MTL instead of the ATF would have avoided the rebuild. So thats what went in the next one. No issues after that.
Peter Kovacs
Property Equity & Mortgage Mgmt
209 345-6708
209 523-4919 fx
----- Original Message ----
From: "JDeRyke at aol.com" <JDeRyke at aol.com>
To: adin at frontier.net; detomaso at realbig.com
Sent: Tuesday, August 5, 2008 3:03:35 PM
Subject: Re: [DeTomaso] Steering rack adventures/ oil specs
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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