While the tests just described permit rating and
screening of gear oils for various purposes, an
illustration of further tests, their result and the
conclusions reached, indicate both the possibility
of extension of full scale and road tests
and also the extreme conditions to which
gear oils can be subjected. Powell and Barton
reported the results of an investigation
relative to the magnitude of tooth loading
in hypoid rear axle gears under normal and severe
operating conditions. For the purpose they used
a 6-cylinder passenger car with
a pre- war torque drive; a drive system
duplicating that of this car on a “T” dynamo meter stand; and Army M-37 truck with
a 4 ton load plus a 1.75 ton
trailed load; and an Army M-211 truck with
a 12 ton load plus a 4 ton trailed load. The
conclusions reached were:
(a) With heavily loaded trucks
the climbing of steep grades can
increase the ring gear torque
as much as 13 to 24 times
that of level road under steady speed.
(b) The addition of trailed loads causes large
increases in gear torque.
(c) The highest gear
loads produced under normal operating
conditions occur as a result of gear shifting.
(d) Engine misfiring resulting
from spark plug fouling causes
repetitive gear loadings equal to the 60
m.p.h. drive side shock in the CRC
L-19 test.
(e) Changes in rate of
throttle opening result in large differences
in the drive side shock loading of
the gears. The substitution of
electric solenoid throttle controls for hydraulic
controls in the CRC L-19 test nearly doubled
the drive side shock torque.
(f) Rate of throttle
closing appeared to have little
effect on the coast side gear shock loads.
(g) Shocks imposed in gear
shifting of heavily loaded trucks on
steep grades produce severe lubrication
requirements by imposing large stepwise
changes of loading on a contact point in
one revolution of the pinion.
