NITRO GEAR & AXLE RING And PINION INSTALLATION GUIDE
We have set up thousands of differentials of all types and would like to share these methods with both the novice and
professional installer. Differential setup is not as difficult as many people assume, but there are strict tolerances and steps that
will ensure a reliable setup. Use this as a guide to assist with installation, but remember it is the installer's ultimate responsibility
to ensure complete and precision installation. This guide covers multiple differential types in addition to Corvette IRS types.
In addition to ordinary sockets, wrenches, etc used for general purpose auto repair, Differential work requires some tools that
are somewhat specialized.
The following tools are recommended:
*Magnetic based Dial indicator
* Dial Calipers
*Hydraulic shop press
*Very strong Impact gun
*Six point Socket set
*Pry bars Short and long
*4 lb sledge hammer
*4-5 lb plastic dead blow hammer
*12-16" long brass drift
*Center punch or number stamp for marking main caps
*Foot lb torque wrench
*Inch lb torque wrench (dial or beam type, nor clicker)
*Die grinder with burr, cut-off wheel, sanding wheel
DISASSEMBLY Integral style with rear cover (Salisbury)
1. Support vehicle or rearend on suitable lift or stands
2. Drain oil by removing cover.
3. Remove wheels, brake drums/rotors/calipers where required.
4. 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 axles nuts/bolts from hub. Slide axles out.
5. Stamp carrier bearing caps as they must be installed in same position as removed. Remove caps.
6. Remove carrier, it may require use of a large pry bar or housing spreader. Keep track of shim locations.
7. Unbolt rear of drive shaft from pinion yoke. Rotate pinion to check for plat 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.
DISASSEMBLY Banjo/3rd member style rear (pumpkin)
1. Support vehicle or rearend on suitable lift or stands.
2. Drain oil by removing drain plug. If no drain plug is present, as with Corvettes, oil will be drained upon removal of 3rd
For corvette, skip to #7
3. Remove wheels, brake drums/ rotors, calipers and/or brake lines where required.
4. Remove axle nuts/bolts from backing plate. Slide axles out.
5. Unbolt rear of driveshaft from pinion yoke.
6. Remove 3rd member.
7. Corvette: Remove rear spring, see factory shop manual for safe spring removal procedure. Disconnect half shafts
from differential side axles, remove strut rods and bracket, support different and remove forward differential mount,
disconnect drive shaft from pinion flange. With differential correctly supported, remove the 2 cross member bolts to
frame, Differential can now be lowered down with attached cross member.
8. Stamp carrier bearing caps as they must be installed in same position as removed. Remove caps.
9. Remove pinion nut. Drive pinion out with large tapered drift, taking care to avoid damage to threads. Remove Races
with brass drift.
10. 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 differential share:
1. Pinion Depth - Is the depth of the pinion in relation in to axle centerline, and is adjusted by adding or subtracting
shims to move pinion in or out. Pinion Depth is verified by tooth contact pattern. Ideal pattern is centered between
Face & Flank. It is important that pinion depth is set correctly to avoid noise and/or gear failure.
2. 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 pinion nut
with a crush sleeve in place, collapsing it until desired preload is achieved.
Pinion Bearing 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.
3. 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 correct lubrication and smooth operation.
4. Carrier Bearing Preload - Is simply how tight the carrier (case - positraction or open) fits in the housing and is set
simultaneously with backlash. On model 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 settings.
Prior to beginning assembly, clean housing, parts, and organize everything that is going to be installed. Verify the new
parts are correct and double check any parts for ware that are being reused. Clear axle housing and remove any
1. Flat file mounting surfaces of ring gear & carrier to remove any burrs or high-spots and clean the Ring & Pinion even
if new to remove machining oil, etc. Apply small amount of oil to inner diameter of ring gear to aid with installation.
Mount ring gear on carrier. Do not use bolts to draw the ring gear on. It is better to start 2 of the bolts as guides, and
use a large dead-blow hammer to drive ring gear on to carrier. Loctite and torque ring gear bolts to spec.
NOTE: Threads must be Clean and free from oily residue or Loctite will not bond !
2. Install Bearings races in housing and press on Pinion & Carrier Bearings. Make sure to keep track of the position &
size of 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 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 or 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.
UPON OBTAINING AN ACCEPTABLE CONTACT PATTERN IT IS TIME FOR FINAL ASSEMBLY.
1. Set pinion bearing preload. Ensure threads are clean with no oily residue. Use Loctite on pinion nut, and a bit of
oil on the washer side. 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
Pinion preload is verified by rotating the pinion with an inch lb torque wrench. For accurate reading use dial or beam
type, (nor clicker). After checking preload, knock pinion from each side to ensure races are seated properly in housing,
then recheck preload.
2. 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.
3. Re-check contact pattern to ensure proper changes have been made.
4. Torque carrier bearing cap bolts to spec.
5. Reassemble in reverse order of disassembly .
6. Follow break-in procedure.