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 for at least one (1) hour, repeat and let cool overnight. Do not drive more than 50 miles at a time until you reach a total of 150 miles..

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 -3 laps at full speed, let cool again for 30 minutes. 2

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 JustRearEnds 9 inches 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

8.              Recommended gear oil: GL-5 80-90 wt non-synthetic. Most 9” rear end use 3 qts.

9.              Clutch Type Positractions (Trac Loc) require a friction modifier additive. Ford # M19546 A or Motorcraft # XL3. You only need one 4 oz bottle.

10. All positraction differentials require BOTH rear tires have the same circumference in order for the differential to work properly without wearing out prematurely.

11. For Ford 8” & 9” Trac Locs:  Always install driver side axle first to avoid misalignment of the split side gears.