How to Install Motive 8.8 in. Front Ring gear and Pinion Set - 3.73 on your F-150

INSTRUCTIONS FOR RING AND PINION SET INSTALLATION

MOTIVE GEAR® HIGHLY RECOMMENDS THAT YOU READ THIS SET OF INSTRUCTIONS COMPLETELY BEFORE BEGINNING THE INSTALLATION OF THIS NEW GEAR SET. CORRECT INSTALLATION CAN BE THE DIFFERENCE BETWEEN A SAFE EXTENDED GEAR LIFE…OR PREMATURE FAILURE.

1. Remove the old gear set and thoroughly clean
both the ring gear carrier and rear end housing
with solvent. After cleaning, air dry all parts and
inspect all components for damage.

2. Verify you have purchased the correct gear
ratio. This can be checked by dividing ring gear
tooth count by the pinion tooth count.

e.g. RING GEAR TOOTH COUNT – 35T
PINION GEAR TOOTH COUNT – 10T
35 ÷ 10 = 3.50:1

3. Many differential cases have many thousands
of miles of service. Check all threads in the
case for wear. It may be necessary to chase the
threads with an engineering tap to clean and align
the threads. When changing case bolts, check to
make sure they are not too long and bottom out in
the ring gear.

4. Check side bearing adjusters as they are often
warped and out of shape, making ring and pinion
settings difficult. Replace as necessary.

5. Check the backside face of the ring gear for
flatness. Generally, after heat treating there may
be a degree of taper. This may be rectified by
lapping gear with sand paper on a glass flat plate.
This will give you a more even and uniform pattern
when setting up your new gear set.

6. Careful attention should be given to blueprinting
your differential. Accurate clearance will lead to a
longer life for your unit. The same care and detail
as used in engine assembly should be exercised.

7. All new parts should be thoroughly cleaned
before assembly and checked for damage. Pinion
bearings should never be removed from the old
pinion and refitted to the new pinion as this may
void any warranties. Always install new bearings.

8. Examine the ring gear mounting surface
for nicks or burrs which might prevent a flush
mounting of the newly installed ring gear. Ring/
Pinion tooth depth variations can result from a
ring gear that is “cocked” on its mounting surface.
If a ring gear spacer is to be used, also check it
for surface imperfections. Nicks or burrs can be
removed by using block-backed grit paper or a
small file. Following material removal, rewash in
solvent and air dry. Mount ring gear. Loctite® ring
gear bolts and torque to factory specifications.

9. All ring gears and pinions have been “LAPPED”
in sets and should never be mixed with another ring
gear or pinion. Check to see that serial numbers
are the same on the ring gear and pinion.

10. Each ring and pinion is pre-run and marked on
the pinion face with its proper depth setting called
the “Checking Distance”. This dimension is from
the face of the pinion to the axle center-line. A
setting tool must be used to measure the checking
distance. Pinion depth is adjusted by adding or
subtracting shim distance. Stay /- .002” of the
pinion dimension (see Illustrations ‘A’ and ‘B’).

11. Once pinion depth is achieved using a new
crush collar or preload shim pack (Dana®), set
pinion bearing preload to 15 inch-pounds rotating
torque with used bearings, and 25 inch-pounds
with new bearings. Once preload is set, install the
seal and Loctite® pinion nut.

12. Once the pinion gear is installed, position ring
gear and carrier into housing to check backlash.
Each ring gear and pinion is developed to run at
.007” to .009” backlash for street gear sets.

13. Adjustments for backlash are done by spanner
rings in the housing or shim packs behind the
carrier bearing cups (GM® or Dana®). Always be
sure carrier bearings are pre-loaded. The carrier
should not fall out of the housing, but should have
to be “tapped” in during final installation. Replace
bearing caps and torque to factory specifications.

14. You are now ready to verify the tooth contact
pattern. A gear marking compound should be used.
Paint gear teeth with compound in several spots
and rotate ring gear several revolutions. A tooth
contact pattern will appear and should be similar to
the pattern shown in Illustration ‘C’. If the pattern is
not in the approximate position shown, reset pinion
depth and backlash to correct pattern. Pinion
shims usually must be moved in .003” increments
to notice a pattern change. If a pattern is heavy
toe, subtract shims (see Illustration ‘D’). If a pattern
is heavy heel, add shims (see Illustration ‘E’).

NOTE: REVERSE THIS PROCEDURE FOR 8” AND 9” FORD®.

15. Fill the case with the required amount of FRESH
80W-90 gear lube. (DO NOT USE “USED” gear lube –
no matter how low the mileage and time on the oil).
Maintain the proper level after the road test as this
may change fluid level. Add as necessary. Proper
maintenance is a must to ensure your safety, as
well as protect the working life of your gear set.

16. Make sure oil vent is not blocked in rear end
housing.

SPECIAL NOTE: IN EXTREME CONDITIONS WE
STRONGLY RECOMMEND A NEW DIFFERENTIAL
COVER THAT HAS AN EXTENDED OIL CAPACITY
FOR NON-REMOVEABLE CARRIER-TYPE REAR
ENDS.

BREAK-IN PERIOD REQUIRED !

-LIGHT DRIVING FOR A PERIOD OF 500
MILES AND NOT AT A CONSTANT ROAD
SPEED (50-60 MPH) FOR ANY RATIOS
LOWER THAN 3.73.

-NO TOWING FOR EXTENDED PERIODS

FINAL RESULTS

Properly maintained and assembled ring and
pinion gears should result in safe and satisfactory
performance. If improperly maintained and/
or assembled, you could experience premature
failure. Be sure the application of your gear set is
the correct one.

WARRANTY

MOTIVE GEAR® warrants that all new ring and pinions supplied by MOTIVE GEAR®, except as otherwise provided herein, will be free from defects in material and workmanship for the first 1 year/100,000 miles whichever occurs first. This warranty will not apply if any part has been modified, damaged, or is defective as a result of any accident, misuse, use in competitive applications, improper installation, negligence,
repair or alteration.

Competition parts are sold “as is”, without any warranty whatsoever. Implied warranties, including warranties of merchantability or fitness for a particular purpose, are excluded. The entire risk as to the quality and performance of such parts is with the buyer. Should such parts prove defective following their purchase, the buyer, and not the manufacturer, distributor or retailer, assumes the entire cost of all
necessary servicing or repair.

This warranty is voided if the ring and pinion is used for competition or if it has been modified. To make a warranty claim on parts used in non-competitive applications, distributors should contact a MOTIVE GEAR® distributor for a Return Goods Authorization (RGA) Number. NO returns will be accepted without an RGA Number. All parts should be returned to MOTIVE GEAR®, freight prepaid. MOTIVE GEAR®
will issue a credit equal to the original purchase price for all defective parts covered by this warranty. In the event that a warranty claim cannot be substantiated by MOTIVE GEAR® , the parts will be returned to the customer, freight collect.

This warranty is in lieu of all other warranties, expressed or implied, including, but not limited to, any implied warranty of merchantability or fitness for a particular purpose, and in no event will MOTIVE GEAR® be liable for incidental, special or consequential damages including, but not limited to, any labor costs.