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DIFFERENTIAL
48-5
8. A continuous low pitch
whirring or scraping
noise starting at
relatively low speed
9. Drive noise, coast noise or
float noise
10. Clunk on acceleration or
deceleration
8. Pinion bearing
9. Ring and pinion gear
10.a. Worn differential cross shaft
in case
b. Engine dash pot out of adjustment
11. Grunt on stops
11. No grease in propeller shaft slip yoke
12. Groan in "Forward" or
12. Wrong lube in differential
"Reverse"
13. Chatter on turns
14. Clunk or knock on rough
road operation
13.a. Wrong lube in differential
b. Clutch plates worn
14. Excessive end play of axle shafts
to differential cross shaft
PRE-REPAIR INVESTIGATION
AND TROUBLE DIAGNOSIS
A close examination of the differential prior to
disassembly will often reveal valuable information as to the
extent and type of repairs or adjustments necessary. The
information thus gained, coupled with the report of
malfunctioning, will provide a basis for determining the
degree of disassembly required. Since frequent cause of axle
noise are improper backlash, pinion bearing pre-load, or side
bearing pre-load, or a combination, a few simple adjustments
may be all that are necessary to correct a problem.
Therefore, before removing the differential from the
housing, the following checks should be made with the results
recorded and analyzed: 1) Backlash; 2) Total Assembly
Preload; and 3) Tooth Contact Pattern Test.
Use care at all times to keep dirt and other foreign
matter, such as grinder dust, soot or sand, away from
differential to prevent possibility of subsequent failure.
The pinion and ring gear must be completely assembled,
installed, and all pre-load and backlash adjustments
completed prior to the start of this method of pinion depth
setting. The following procedure can be used in place of the
gage method of pinion depth setting.
GEAR TOOTH NOMENCLATURE
The side of the ring gear tooth which curves outward,
or is convex, is referred to as the "drive" side. The concave
side is the "coast" side. The end of the tooth nearest center
of ring gear is referred to as the "toe" end.
The end of the tooth farthest away from the center is the
"heel" end. Toe end of tooth is smaller than heel end. It is
very important that tooth contact be tested before the
differential carrier assembly is disassembled. Variations in the
carrier or pinion rear bearing may cause the pinion to be too
far away from, or close to, the ring gear. Thus, the tooth
contact must be tested and corrected, if necessary, or the
gears may be noisy.
TOOTH CONTACT PATTERN TEST
1. Wipe oil out of carrier and carefully clean each tooth
of ring gear.
2. Use gear marking compound and apply this mixture
sparingly to all ring gear teeth, using a medium stiff brush.
When properly used, the area of pinion tooth contact will be
visible when hand load is applied.
3. Tighten bearing cap bolts to 55 Ib. ft.
4. Expand brake shoes until a torque of 40-50 lb. ft. is
required to turn the pinion.
A test made without loading the gears will not give a
satisfactory pattern. Turn pinion flange with wrench so that
ring gear rotates one full revolution, then reverse rotation so
that ring gear rotates one revolution in opposite direction.
5. Observe pattern on ring gear teeth and compare with
Figs. 4B-3.
EFFECTS OF INCREASING LOAD ON
TEETH CONTACT PATTERN
When "load" on ring and pinion gear is increased, such
as when car is accelerated forward from standstill or from
normal drive, the tooth contact will tend to spread out and,
under very heavy load, will extend from near toe to near heel
on the drive side. The entire contact also tends to shift toward
heel under increasingly heavier loads and will become
somewhat broader with respect to tops and bottoms of teeth.
The patterns obtained by this tooth contact pattern test
approximate a light load and, for this reason, they will extend
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