Contour Enthusiasts Group Archives Forums Modifications Transaxle Watch out

Terry just sent me this. He's been discussing the issue with some colleagues that work as "lube" engineers.

....info so far from 'Karl'(Germany),'Mike' (UK) &
'Ryan' (USA).
The overall take is that 'GL' additives are all a
problem in a trans with a)ally case b)brass bronze
blockers etc.The majority of GL additives are sulphur
based.This varies in %'age but does have a corrosive
effect on the brass blockers,be it slow.All agree that
the 'grey'/black paste is a result of the additives on
the ally case causing oxide.
ATF fluids dare not have any sulphur additive due to
the paste (re valve bodies in autos)and a lot of autos
also use brass/bronze bushings.
It appears the guts of the problem is sulphur.
Points against ATF...it does not like high gear tooth
pressures and can break down in high tooth pressure
designs(Re straight cut,semi-helical & hypoid gear
cuts),the MTX 75 has helical gear cut(lower tooth
pressures),except in the 'stoc' open diff gears ,which
are straight cut.This may expalain why some owners
feel the HP lube may save the diff gears.Should add my
2 cents here that the pre 98 diffs were 'fully' cut
gears Vs the later moulded/sintered diff gears.I have
never seen the early 'cut' gears fail,a diff pinion
pin yes but not the gears and most of these have run
straight ATF all the time (it was factory fill).
Examples ,an MTX with stoc gears and a Quaife/Torsen
diff = ATF or current Ford spec honey.
An MTX with Quaife 'syncro' gear set(which have a
semi-helical gear cut) and a Quaife diff =75W90
G4....this shows that the gear tooth pressure on a
semi-helical cut needs EP additives plus you will get
some grey residue but the EP is for the main gears not
the Quaife/Torsen diff.
Last extreme would be a Quaife 'dog gear' set that has
straight cut gears,no brass blockers(uses steel dogs')
and a Quaife diff =75W90 GL4/5, a higher GL rating for
the even higher gear tooth pressures of a straight cut
gears over a semi-helical or helical cut.
We still have some more info from all three to
come....Just a point to note,the MTL spec sheet on
it's benefits list *Satisfies manual transmissions and
transaxles requiring motor oils(engine) or GL-1,GL-3
or GL-4 gear oils. The MTX75 has never been spec'd
with motor oils or any GL type gear lubes,the only two
lubes have been ATF then 'honey(as a retro fill back
to '95)...