Adjusting Backlash; Measuring Backlash; Gear Tooth Contact Pattern Check; Gear Tooth Terms - GMC T Series 1994 Repair Manual

ADJUSTING BACKLASH

Tools Required:
J 8001 Dial Indicator Set
1. Refer to figures 1 through 4.
2. Tighten the right sleeve (32) to 140 N-m (100 lbs.
ft.) using J 36599 (figure 28).
3. Tighten the left sleeve (32) (K1, 2 models) or
adjuster plug (61) (K3 models) to 140 N-m (100
lbs. ft.).
• Use J 36599 (K1, 2 models) (figure 28).
• Use J 36615 (K3 models) (figure 29).
4. Mark the location of the adjusting sleeves in rela­
tion to the carrier halves, so the notches in the
adjusting sleeves can be counted when turned.
5. Turn the right sleeve OUT two notches.
6. Turn the left sleeve (K1, 2 models) or adjuster plug
(K3 models) IN one notch.
7. Rotate the pinion several times to seat the bear­
ings.

MEASURING BACKLASH

1. Install a dial indicator so the button contacts the
outer edge of the pinion flange. The plunger must
be at a right angle to the pinion flange (figure 31).
2. Move the pinion flange through its free play while
holding the differential carrier. Record the dial indi­
cator reading.
3. Divide the dial indicator reading by 2 to obtain the
actual backlash when using this method. Example:
A dial indicator reading of 0.16 mm means that
there is actually 0.08 mm backlash.
4. Follow the steps for adjusting backlash.
• Gear backlash should be between 0.08-0.25
mm (0.003-0.010 inch) with a preferred specifi­
cation of 0.13-0.18 mm (0.005-0.007 inch).
• If the backlash is incorrect, adjust the sleeves
as necessary. Always maintain the " one notch"
preload on the side bearings. Example: If it is
necessary to turn the RIGHT sleeve IN one
notch, the LEFT sleeve must be turned OUT
one notch.
• To increase backlash, turn the left sleeve in,
and turn the right sleeve out an identical
amount. To decrease backlash, turn the right
sleeve in and turn the left sleeve out an identi­
cal amount.
• Changing the sleeves one notch will change
backlash about 0.08 mm (0.003 inch).
GEAR TOOTH CONTACT
Before final assembly of the differential, a gear tooth
contact pattern check should be performed.
A gear tooth contact pattern check is NOT a substi­
tute for adjusting pinion depth and backlash as previ­
ously outlined. It is a final check to verify the correct
running position of the ring gear and the drive pinion.
Gear sets which are not positioned properly may be
noisy, or have a short life, or both. With a pattern
check, the best contact between the ring gear and the
drive pinion for low noise level and long life can be
ensured.

GEAR TOOTH TERMS

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. The toe end of the tooth is smaller
than the heel end (figure 32).
F5875
PATTERN CHECK