1. Any overloading or overheating will cause the oil to break down and the ring and pinion will fail.

2. A ring and pinion installation, especially a high numeric ratio with new bearings, can cause an excessive heat build up in the rear end and cause softening of the gear teeth and bearings if a break in is not performed.

3. To break in the installation, perform a run-in prior to driving, with the rear wheels jacked up and operating at idle speed in high gear for a minimum of five (5) minutes. Drive vehicle 10 miles at a normal speed, let cool one (1) hour, repeat, once.

4. Vehicles used for towing need approximately 200-300miles of normal street driving BEFORE being used for towing.

5. On circle track race cars, make approximately 6-8 laps at slow speed, then let cool for 30 minutes, make 6-8 laps more at slow speed, then 2-3 laps at full speed. Let cool again for 30 minutes.

6. Drag cars need only an initial run-in since they are driven short distances and heat is not normally a problem with proper lubrication and backlash allowances.

7. All Just Rear Emds 9 inch differentials use a solid spacer in place of the stock crush sleeve. This is not only stronger, but facilitates the replacement of the pinion yolk and/or seal without affecting pinion bearing preload.

Special Notes

A. For Ford 8”and 9” Trac Locs, always install driver side axle first to avoid misalignment of the split side gears.

B. Recommended gear oil: GL-5 80-90 wt NON-SYNTHETIC.

C. Positractions require a Ford or Motorcraft friction modifier additive. Part number: M-19546A.