Fordnatics List Archive

This read-only message was archived from a public mail list.
Mail From: (email redacted) (Scott Griffith, Sun Microsystems Lumpyware)

On Nov 8, I wrote:

> On Nov 8, Brad White wrote:
>
> > 2) one post mentioned Sulfur in the Ford synth. tranny fluid, and
> > this might be bad. Any further comments on this?
>
> I have a call in to the Borg-Warner engineering hotline
> to ask exactly that. They haven't returned my call yet, but as soon
> as he does, I'll let the list know.

I got my call back from Borg-Warner, and got a lot of my questions
answered. I'll relay the high points here, and then try to put
together a better (longer) article for my club newsletter when time
permits. But here are the high points:

All T-5s are designed and spec'd for ATF, as we knew. All T-5s, except
for those shipped to GM for one year for the F-bodies, were factory
filled with ATF. That one year of GM boxes was filled with 30W motor
oil, but they switched back the next year. The older (pre-"World
Class" T-5s with the brass synchro rings could also tolerate light
(Gl-1/2) gear oils, but the best performance is still achieved with
the higher-Cf ATFs.

The more recent "World Class" T-5s with the carbon-fiber blocker rings
have a friction material bonded to their working surfaces that is very
similar to the friction material used in automatic transmission
clutches. Certain EP additives used in some GL-4 and GL-5 gear lubes
can attack the bonding materials and damage the synchro rings. The
Borg/Warner rep wouldn't say positively what those additives were, or
which oils, but I gather that they are the sulfur-bearing EP additives
that are absent from Dexron-II ATFs.

Use of extremely slick lubricants, such as the GL3/4/5 gear oils, will
also lead to premature synchro wear even with the older brass
synchros. This is caused by the lower Cf of the gear oils reducing the
oil-film friction that is required for the operation of the synchros.
The Borg/Warner rep said that use of a slick GL-5 oil will probably
result in very noisy shifts and synchro damage in very short order, as
the driver overpowers the balky and slow synchronization process by
simply pulling harder, resulting in synchro clash. He said that the
vast majority of the calls the B/W troubleshooting line gets are from
owners who have had gear oil put in their gearboxes by overly-helpful
and undertrained quick-lube technicians (Note: I *didn't* prompt him
on this one!), and suddenly noticed that the damned thing wouldn't
shift decently any more.

The use of any friction modifier additive in the lubricant that is
intended to make the oil more slippery will have much the same bad
effect on the synchros, and will slow down the shifting process and
speed up the wear in the synchros. He was very insistent that adding
in a friction modifier was a Bad Idea.

The Borg/Warner rep would not comment on synthetic lubes for the T-5,
whether they were ATFs or any other lubricant, such as the Red Line
MTL or the Merkur synthetic tranny fluid. The party line from the
manufacturer is "Dexron-II ATF, period". They have not tested or
approved any synthetic gear oils for use with the T-5. We all know
that many folks use synthetics with very good results, but he was
adamantly neutral about them. The direct quote was "You're on your
own."

He did tell me an interesting story about qualifiying a synthetic
75W90 gear oil in the T-56 six speed for racing use, however, and
related that they had good results in that very different and very
high-temp application. I don't know what the blocker ring design is
for that 'box. I'll have to ask him next time.

Conclusions: Dinosaur and synthetic ATFs that meet Dexron II specs are
the safe bet. Red Line MTL also has the higher coefficient of friction
that will make the synchros happy, and may also work for you if your
religion calls for it (although once again, the B/W rep wouldn't say
either way). Gear oils with sulfur EP additives, whether they're
called GL-3, GL-4, GL-5, or Gorilla Snot, are *not* acceptable in the
World Class 'boxes, as synchro damage will occur.

This is a quickie aside for those who've run both MTL and ATF in their
T-5s, and wonder why they feel so much different. The MTL is very
viscous with respect to the ATFs, especially cold. It has excellent
properties in the synchros, allowing them to match speeds very
quickly, but then its viscosity makes the synchros actually slide home
much more slowly (especially if the 'box is new and tight). It will
behave well at the high temperatures found in roadracing use, but will
probably feel quite stiff at street speeds and temps, especially in
the dead of winter.

Thus, MTL _may_ make sense in all-out race use, or in an older box, or
one that's seen some abuse and has opened up the clearances in the
synchros. And if you're running MTL and find the box to be a bit stiff
for your tastes, you might consider trying one of the synthetic ATFs.
You can tune the viscosity and Cf of the fluid to get different feels.
I finally got the Red Line technical product data sheets, and here's
what I found:

Fluid Viscosity, 40degC Viscosity, 100degC
(Centistokes) (Centistokes)

Red Line MTL 50.8 10.2
Red Line High-Temp ATF 64.1 11.8
Red Line Racing ATF (TF) 63.1 10.0
Red Line Synthetic ATF 32.5 7.2
Mobil 1 Synthetic ATF 29 5.7
Mobil Multi-Purpose ATF 37.6 7.0
Mobil ATF 210 (Type F) 38 7.5

You can see that the Red Line stuff is a great deal stiffer,
especially cold. For those of us who do most of our driving *below*
race temperatures (say, 250-325degF), that can explain the stories of
"balky shifting" that come around now and again.

Gotta try that stuff someday, now that my 'box is broken in (120k
miles...). I also have every intention of trying some of Red Line's
"Shock Proof" synthetic 75W140 gear oil in the rear end for next
season. Lots of new soups to pour on the floor...

-skod

- --
Scott Griffith, Sun Microsystems Lumpyware
expatriate SCCA New England Region Flagging/Communications worker
(and driver, of anything that turns both right and left,
and can pass tech...) Return Path : (email redacted)