While a single lubricant for both
transmissions and rear axles of certain automobiles is desirable, Hunsted et
al.^28 ,when reviewing the situation with regard to such fluids, concluded that as of January
1960 considerable work remained
to be done on transaxle fluids to achieve optimum results. Up to
that time some
42 mineral oil base and synthetic base fluids, with
various additives, had been
evaluated and only three
showed any promise
for future development. Since it is
impractical to suggest even
tentative formulations, all
that can be done is to
indicate the requirements and the handicaps.
A
transaxle fluid should
have all the
desirable characteristics of ATF and
in addition should
have sufficient EP value
to lubricate hypoid
gears. The above statement should be modified in that the desirable
characteristics of ATF should also be maintained while in service. Thus,
when the
fluid is subjected to the
shear effect of mating gears, polymer type additives may
lose a large part
of their effectiveness due
to breakdown of the
polymers to lower molecular weight products. Therefore base
fluids with inherent high
V.I. or polymers of initially
lower molecular weight are
dictated in the formulations.
EP agents used
should have no adverse
effect on any of the
components of the automatic
transmission such as clutch
materials, various metals,
synthetic seals, etc. Of course the most
desirable transaxle fluid would
be one which
could be sealed
in a case and serve the
life of the car
but first a
fluid which will perform satisfactorily when changed
periodically will serve.
According to Celanese
a trimethylolpropane ester
with an EP additive offers promise for use
as a transaxle fluid. Another
suggestion for the purpose is methylchlorophenyl containing about 3 per cent
chloride.
