Since the lubrication of transmissions and axles
is of primary importance in automotive vehicles,
as gearing is concerned, this subject will have first
consideration. Mention of the lubrication of other gear sets in such
vehicles will then follow:
Also the major discussion will
consider internal combustion engines as a source of power. Other
sources of power and methods other than gearing
for driving vehicles and the consequent fluids
require will also receive mention. Gearing or transmission
mechanisms of automobiles, buses or trucks are
lubricated, in the main , by bath or splash
systems with some use of forced feed. The
gear cases are generally as small as
possible so that consequently the amount of gear
oil present is restricted. While the fluids
present in gear boxes may have other uses, the
primary functions are to prevent wear of
gears and to act as a heat transfer
medium. The general subject of wear
prevention has been discussed previously and
may be due either to the oil film
alone or to this fluid supplemented by EP films.
The oil in gear cases of vehicles takes up
heat from the moving gears and transfers it
to the inside of the casing. Form here it is dissipated to the
surrounding air. Such radiation is not always what
is desired because the gear housing becomes
coated with dust or dirt. Consequently, particularly
in heavy trucks and busses, the temperature of
the lubricant may reach 250 to 300 degree F
causing excessive oil deterioration.
The loads,
speeds, conditions of use and the operators of
vehicles vary so widely that it is a wonder
that automotive gears give such long and
trouble free operation as they do in most cases. The
service obtained from such gearing is probably more of
a tribute to the people who formulated and supplied
the lubricants than to the designers
of the mechanisms. In fact Raymond, a few years ago, stated: “
The hypoid axle is easily the hardest
working and possibly one of the most
neglected automotive components”. Elsewhere the
thought was advanced that gear oil manufacturers have
been asked to perform miracles, in order to lubricates such
gears.
