B - Front Drive Axle Diagnosis and Repair
1. If all torque readings obtained in Section A, 2a and 2b, are 2.8 N.m (25 lb-in) or less, the differential side gear thrust washers DO NOT need to be replaced. Proceed to Section B, Step 2.
If any of the torque readings through the differential obtained in Section A, 2a and 2b, were over 2.8 N.m (25 lb-in), replace the two (2) flat differential side gear thrust washers (Figure 2) with the 0.635 mm (0.025") thick washers supplied with the Axle Motoring Torque Reduction Kit (F6TZ-4228-BA). Follow the procedure listed in the appropriate year F-Series/Bronco Powertrain/Drivetrain Service Manual, Section 05-03A for differential and carrier removal instructions.
2. If any of the torque readings through the pinion (opposite axle held) obtained in Section A, 3a and 3b, are over 6.8 N.m (80 lb-in), measure the pinion bearing pre-load to determine if the pinion should be re-shimmed using the Axle Motoring Torque Reduction Kit (F6TZ-4228-BA).
a. Follow the procedure listed in the appropriate year F-Series/Bronco Powertrain/Drivetrain Service Manual, Section 05-03A for differential and carrier removal instructions.
b. While the differential assembly is out of the axle housing, check the pinion for smooth, pulse-free rotation.
c. Slowly rotate the pinion in the carrier using a dial or beam-type inch-pound torque wrench. Stop at the highest reading, then restart and record the breakaway torque reading. Measure and record the torque required to rotate the pinion.
d. If the breakaway torque is more than 0.7 N.m (6 lb-in) greater than the torque to rotate and/or the pinion rotation is not smooth and pulse-free, inspect the pinion bearings for cage deformation and/or irregular roller or cup wear patterns. Replace the bearing (4621-outer, 4630-inner) if either condition is found.
NOTE:
USE OLD PINION NUT AND WASHER TO ESTABLISH THE SHIM PACK REQUIRED FOR REDUCED PINION TORQUE TO ROTATE. ONLY USE NEW PINION NUT AND WASHER AFTER REQUIRED SHIM PACK HAS BEEN ESTABLISHED.
e. If the pinion torque to turn is greater than 2.3 N.m (20 lb-in), adjust the shim pack (using the shims provided in the kit) so that pinion torque to turn is 1.7 N.m (15 lb-in). For each thousandth of an inch added to the shim pack, the torque to rotate the pinion will decrease by approximately 0.9 N.m (8 lb-in).
WARNING:
DO NOT ALLOW ANY PINION END PLAY IN THE PINION BEARING ADJUSTMENT.
f. While the axle shafts are out of the axle assembly, inspect the U-joints for freedom of movement and replace if seized.
CAUTION:
DO NOT USE 80W90 OR 90W GEAR LUBE.
g. Reassemble the front drive axle following the procedure listed in the appropriate year F-Series/Bronco Powertrain/Drivetrain Service Manual, Section 05-03A for differential and carrier installation instructions. Replace the pinion nut and washer with those supplied in the kit. If the ring gear was removed from the differential, replace the ring gear bolts with those supplied in the kit. Fill the axle assembly with 4X4 Gear Oil (F1TZ-19580-A or equivalent meeting Ford specification WSL-M2C191-A).
h. Recheck torque reading in Section A, Step 2a to verify that axle modifications have been performed properly.
i. Return the vehicle to the customer and ask the customer to drive the vehicle for 80 km (50 miles) with the hubs locked to "break-in" the modified axle. To break-in axle, engage four-wheel-drive, drive forward, and then shift out of four-wheel-drive without disengaging the hub locks. If the vehicle is backed up during this time period, the hub locks will disengage and will have to be engaged again by repeating this procedure.
If this procedure has not resolved the concern, call the Self-Engagement Hotline at 1-503-786-5486 (Monday-Friday, 10:00 AM-6:30 PM Eastern Time).