The professionals at Nitro Gear & Axle have setup
thousands of differentials and would like to share their methods with both the
novice and professional installer. Differential building is not as mysterious
as many people assume; however, there are strict tolerances and critical steps
to ensure a reliable setup. This guide is a reference to help with
installation, but remember it is the ultimately the installer’s responsibility
to ensure a precise and complete installation.
In addition to ordinary sockets, wrenches, drifts, safety
glasses, ear protection, etc. used for general auto repairs; differential work
requires tools that are somewhat specialized.
The following tools are recommended:
Dial indicator with magnetic base
Dial calipers
Bearing puller
Hydraulic shop press
Very strong impact gun
Six point socket set
Pry bars, short & long
Steel hammer
4 lb. sledge hammer
4-5 lb. plastic dead blow hammer
12"-16” long brass drift
Center punch or number stamp for marking caps
Oil drain pan / tray • Foot lb. torque wrench
Inch lb. torque wrench (dial or beam style, not clicker)
Die grinder with de-burr, cut off and sanding wheels
DIS-ASSEMBLY:Integral styles with rear cover (aka Salisbury)
Support vehicle or rear-end on suitable lift or
stands.
Drain oil by removing differential cover.
Remove wheels, brake drums, rotors and/or calipers where
required.
Remove axle shafts.
a.
C-Clip: Remove cross pin shaft retainer bolt and cross pin shaft. Push axles inward to remove c-clips. Remove axles.
b. Bolt in: Remove axle
nuts/bolts from backing plate. Slide axles out (may require slide hammer)
c.
Full float: Remove axle nuts/bolts from hub.
Slide axles out
Stamp carrier bearing caps as they must be installed in
same position as removed. Remove caps.
Remove carrier, it may be necessary to use a large pry
bar or housing spreader. Keep track of
shim locations.
Unbolt rear of driveshaft from pinion yoke. Rotate pinion to check for play or
roughness. Remove pinion nut. Drive
pinion out with large tapered drift, taking care to avoid damage to threads
8. Organize and inspect all parts for damage or wear.
Remove axle nuts/bolts from backing plate. Slide axles
out.
Unbolt rear of driveshaft from pinion yoke.
Remove 3rd member.
Stamp carrier bearing caps as they must be installed in
same position as removed. Remove caps.
Remove pinion nut. Drive pinion out with large tapered
drift, taking care to avoid damage to threads
Organize and inspect all parts for damage or wear.
Critical Areas of Setup:
Although there are many steps to differential repair, there
are 4 critical areas of setup that all differentials share:
Pinion Depth – Is the depth of the pinion in relation to
axle centerline, and is adjusted by adding or subtracting shims to move pinion
in our out. Pinion Depth is verified by
tooth contact pattern. Ideal pattern is
centered between Face & Flank. It is
important that pinion depth is set properly to avoid noise and/or gear failure.
Pinion Bearing Preload - Is the amount of rolling
resistance on the pinion bearings. This
is adjusted by adding or subtracting shims located between pinion bearings
(more shim = less preload) alternatively set by tightening nut with a crush
sleeve in place, collapsing it until desired preload is achieved. Pinion Preload is verified by rotating the
pinion with an inch lb. torque wrench.
It is important preload is within spec.
Pinion bearings will fail quickly if over-preloaded.
Backlash – Is the free-play between the ring &
pinion. Backlash is adjusted by moving
the carrier left or right with shims or adjuster nuts on the sides of the
carrier, and checked with a dial indicator by rocking the ring gear by
hand. It is important backlash is within
spec to allow smooth operation and proper lubrication.
Carrier Bearing Preload – Is simply how tight the carrier
fits in the housing and is set simultaneously with backlash. On models with shims, carrier bearing preload
is increased by adding overall shim thickness.
On models with adjuster nuts, carrier bearing preload is increased by
tightening the adjusters. Carrier
bearing preload is important for a strong setup. If preload is too loose you will be more
likely to spin bearings and/or break gear teeth.
Carrier preload tip: If backlash is within spec, but preload
is too loose you can add equal amounts of shim thickness to each side of the carrier,
or on tighten adjuster nuts equally.
This will increase preload, while maintaining backlash setting.
ASSEMBLY:
Prior to beginning assembly, clean housing, parts, and
organize everything that is going be installed.
Verify the new parts are correct and double check any parts for wear
that are being reused. Clean axle
housing and remove any debris.
Flat file mounting surfaces of ring gear & carrier to
remove any burrs or high-spots and wash Ring & Pinion, even if new, to
remove cosmoline, etc. Mount ring gear on carrier. Do not use bolts to draw the ring gear
on. It is better to start 2 of the bolts
and use a large dead-blow hammer to drive ring gear on to carrier. Loctite and torque ring gear bolts to spec.
Install
Bearing races in housing and press Pinion & Carrier Bearings. Make sure to
keep track of the position & size of any shims, baffles, or slingers if/where
applicable.
INITIAL TRIAL ASSEMBLY:
Note: It is usually best to use stock shim thickness for a
starting point.
1. Install Pinion & tighten nut until there is no slop
and a bit of preload. Actual preload
will be set later during final assembly.
It is recommended that the initial assembly be done without crush sleeve
as they are a single-use item.
2. Install carrier/ring gear assembly & set Backlash-
Carrier should be snug in order to obtain an accurate reading. It is best to measure with indicator needle
perpendicular to the Drive side of the ring gear teeth. Backlash should be close to spec, even for
trial assembly. Measure in a few spots
to check for variance/run-out. Backlash
is adjusted by moving the carrier left or right with shims or adjuster nuts on
the sides of the carrier, and checked with a dial indicator. To increase backlash on models with carrier
shims, shim thickness will be decreased on the ring gear side and added to the
opposite side of the carrier and vice versa. To increase backlash on models
with adjuster nuts, the adjuster on the ring gear side is loosened, and the
opposite adjuster is tightened. Backlash
tip: Shim thickness changes of 0.010” will generally effect backlash by roughly
0.007”. For example, if backlash is
measured at 0.002” and the desired spec is 0.006”-0.010” you would remove
0.010” from the ring gear side of the carrier and move it to the opposite
side. This will move the ring gear away
from the pinion and should increase backlash to about 0.009”.
3. Check Pinion
Depth- Apply marking compound to ring gear and rotate back and forth through
the pinion to obtain a contact pattern.
The contact pattern will indicate the depth of the pinion in relation to
axle centerline, and is adjusted by adding or subtracting shims to move pinion
in our out. On models with depth shim
located under pinion bearing or pinion race: Adding shim will move pinion
deeper causing pattern to approach Flank.
Subtracting shim thickness will move pinion further away, causing
pattern to approach Face. See Pattern
Example photos. NOTE: On models with
removable pinion support like GM 14T, Ford 8”, 9”, subtracting shim will move
pinion deeper and VS. VS.
FINAL ASSEMBLY:
Upon obtaining an acceptable contact pattern it is time for
final assembly.
Set pinion bearing preload: Ensure threads are clean with no oily residue;
Use red loctite on pinion nut, and a bit of oil on the washer surface. Also apply grease to seal.
A. Models with Preload shims: Pinion preload is adjusted by
adding or subtracting shims located between pinion bearings (more shim = less
preload) and vs. vs. Reading should be
taken with nut all the way tight.
B. Models with Crush sleeve: Pinion preload is adjusted by
tightening nut with a crush sleeve in place between bearings, collapsing it
until desired preload is achieved. NOTE:
Do not exceed preload spec or you must use a new crush sleeve.
Pinion Preload is verified by rotating the pinion with an
inch lb torque wrench. For accurate
reading use dial or beam type. (not clicker).
After checking preload, knock pinion from each side to ensure races are
seated properly in housing, then recheck preload.
Install carrier
assembly. For final assembly it is
important that there is preload on the carrier.
Follow the same steps detailed above for checking & setting
backlash. TIP: On models with carrier
shims – If carrier preload was loose but backlash was within spec add an equal
amount of shim to each side prior to installing. The carrier should be very tight. On models that use shims, it should require a
pry-bar to remove the carrier, if the carrier simply slides out, you need more
preload.
Re-check contact pattern to ensure proper changes have
been made.
Torque carrier bearing cap bolts to spec.
Reassemble in reverse order of dis-assembly.
6. Follow break-in procedure.
BREAK-IN PROCEDURE:
In order to prevent damage to differential
components it is essential to follow the break-in procedure after installation
of a new ring & pinion. New ring & pinions will generate more
heat initially after installation and can cause gear oil to break down, leading
to premature failure. On your first
drive, stop after the first 15 or 20 miles and let the differential cool for
20-25 minutes before proceeding. Drive conservatively for the first 500 miles
following installation (avoid hard acceleration & towing). After completing standard break-in, tow for
very short distances (less than 15 miles) and let the differential cool before
continuing during the first 45 towing miles. Change the gear oil after the
first 500 miles. This will remove any metal particles or phosphorus coating
that has come from the new ring & pinion.
Premature
overloading/overheating will cause gear oil to breakdown, and may result in
parts failure.
