1935 Cadillac - GM Heritage Center

31
REAR AXLE
A ring gear and drive pinion are shown in Fig.
12, Plate 7, set in the proper running position, and
in this position all tooth dimensions, theoretically,
converge to cone center "A." In this position,
only the pitch lines of the ring gear and drive
pinion coincide; and although all other proportions
of tooth shape converge toward the cone centers
of the gears, they are in no place parallel to the
pitch line.
It is, therefore, evident that the shifting of gears
from the correct position, results in throwing the
pitch lines out of parallel and changing the contact
of the gear and pinion from a full contact toward
either the toe or the heel of the ring gear. (See
Figs. 14 and 15, Plate 7). If the ring gear is moved
away from the drive pinion the contact is moved
toward the heel; if the gear is moved closer to the
pinion, the contact is moved toward the toe of the
gear teeth. The reason for this is that when the
ring gear is moved away from the pinion the heel
of the tooth will be last in mesh. If the gear is
moved toward the pinion, the backlash or clearance
is first taken up at the toe.
Before an attempt is made to adjust the gear
mesh, the rear axle lubricant should be drained and
the gears cleaned.
Adjustment of Drive Pinion
An initial adjustment may be made on the Cadillac
drive pinion when putting the differential and
pinion assembly together by installing the proper
number of shims between the front pinion bearing
retainer and the front end of the differential
carrier. Use sufficient shims to give a total thickness
of .075 to .090 in. These shims are supplied
by the factory Parts Division in thickness of .010
in., .015 in. and .035 in.
The LaSalle driving pinion is adjusted by means
of threaded nuts instead of shims. Turning these
nuts (use Tool No. HM-575 on front nut) in a
clockwise direction, as viewed from the front,
moves the pinion rearward toward the ring gear
and turning them in a counter-clockwise direction
moves the pinion frontward away from the ring
gear. When making this adjustment back off the
leading nut one or more notches and tighten the
trailing nut an equal amount.
The final adjustment of the drive pinion is made
according to the tooth contact as explained under
"Testing Ring Gear for Proper Tooth Contact."
Adjustment of Differential Side Bearings
To adjust the differential side bearings, it is
necessary first to remove the locking plates for the
adjuster rings and to loosen the bearing caps
slightly. The adjusters are then turned to tighten
the bearings so that a pull of 8 to 10 pounds,
measured at the circumference of the ring gear, is
required to turn this gear. This test can be made
with a spring scale hooked on one of the ring gear
teeth as shown in Fig. 16. An initial pull of about
15 pounds will be required to start the gear, but
as soon as it is started the pull should drop to 8 to
10 pounds.
Fig. 16. Checking adjustment of differential side
bearings. A pull of 8 to 10 pounds should be required
to turn the ring gear.
After the adjustment is completed, the bearing
caps must be tightened and the locking plates
installed.
Adjustment of Ring Gear
The adjustment of the ring gear is made by
moving the ring gear and differential case sideways.
This is accomplished by turning the
adjuster rings for the differential side bearings an
equal amount as required. Although the ring
gear tooth contact is the next important consideration,
the backlash should be checked before
checking for tooth contact, as both backlash and
tooth contact are controlled by the same adjustment
and backlash must be kept within the specified
limits of .004 to .012 in. on the Cadillac while
adjusting the tooth contact.
The amount of backlash necessary to give the
proper tooth contact with the pinion adjustment
correctly made on the LaSalle is etched on the end
Fig. 17. Checking backlash between ring gear and
drive pinion with dial indicator and holder, tool No.
HM-91220. Backlash should be .004 to .012 in. in Cadillac
cars. On LaSalle cars the amount of backlash
should correspond to the number etched on the end of
the pinion gear.