How to set up a differential

by Contributor

Replacing a differential carrier, changing bearings or a ring and pinion can be a challenging process. Adjusting it to just right for a long life and quiet operation is the most difficult part of the repair.

Determine the problem and replace damaged or worn parts. If ring and/or pinion gears are worn they will have to be replaced as a matched set.

Use matching feeler gauges to determine clearance

Measure side gear clearance and adjust with select shims. Assemble without any shims, determine total amount of clearance and divide by two, this will be your shim thickness.

Pinion depth will need to be determined next, this is the variance between the difference of the machined pinion gear and the difference of the housing where the gear is installed. You will have to add or remove shims in your axle depending on type and what your measurement is.

Gm and Chrysler Pinion depth adjustment.

Ford Pinion depth adjustment.

Once pinion depth is achieved install new seal, loctite pinion nut, and using a new crush collar set pinion bearing preload to 15 inch-pounds rotating torque used bearing, and 25 inch-pounds with new bearings. You check rotating torque by installing the inch pound torque wrench and turning and reading the wrench. You a beam type or dial type torque wrench for this.

Next install the differential carrier, this is the part that the ring gear is bolted to. If it has the adjustable nuts on the side bearings, then this is the easy system to set up, but you will need special wrenches to go through the axle housing to make the adjustments. They look like a long bar with nuts on the ends.

If your differential is the shim type you will need to use a case spreader to take the pressure off of the side bearings to remove and install the center carrier assembly. Use a dial indicator when spreading the housing and don't over spread or the housing will be damaged.

Determine side gear bearing preload first, then adjust backlash by adding or removing shims from one side to the other or by adjusting center carrier bearing nuts from one side to the other until the desired backlash is obtained.

Once backlash and carrier bearing preload is set, then you will want to do a pattern check to see where the tooth contact is, desired is in the middle and lower on the tooth. Paint a contact solution or prussion blue on the face of the teeth, apply resistance on the ring gear and rotate the pinion gear until you have completed one full revolution of the ring gear in both directions (drive and coast)

Tooth contact chart

Compare your readings to a chart and see if re-adjustment is needed.

Install your axle shafts, cover and fill with the correct lube to the fill plug hole (just where it starts to come back out) Make sure your axle vent is open, usually located on top of the housing. Road test and verify your repair.

A new ring and pinion installed with new bearings will initially generate higher than normal operating temperatures. It is advisable to use whichever of the following break in procedures matches your application. 1. With vehicle still on jack stands and rear-end filled with proper amount of lube, run in forward and reverse approximately 2 to 3 minutes. 2. Drive vehicle approximately 10 miles at normal operating speeds. Accelerate and decelerate several times conservatively, then let cool. 3. Do not do any heavy towing for 300 miles.

Tip

  • check Take your vehicle to a well qualified technician if you don't understand what you are doing.

Warnings

  • close Always use jack stands when working under vehicles
  • close Work on a hard flat surface

Items you will need

About the Author

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