1. A good "rule of thumb" method for turning your gearing to the desired RPM is this example:
Joe Racer is turning the engine 6000RPM at the end of the straight away, he would like to turn at 6800 at the end of the straight, now he is running a final drive of 5.04. Work the math this way:
6800 / 6000 = 1.13
1.13 x 5.04 = 5.70
5.7 would be the gear of choice.
2. If you break a set of quickchange gears, you must check the lowershaft for runout. 1-3 thousands is maximum.
3. In the heat of action at the race track, everybody always overtightens the rear cover bolts, the proper torque is 18 ft. lbs. for an original. 25 ft. lbs. if you torque a cover using a stud and nut.
4. Formula to Compute Final Drive
Small gear teeth number divides large gear teeth number equal spur ratio times ring & pinion equals final drive.
Example Set Number 18: 29 ÷23 = 1.263 x 4.86 = 6.13
Ratio x MPH x 336 = RPM RPM x Tire Dia. = Ratio
Tire Dia. MPH x 336
5. Beware of the oil used with a lightweight spool. A spool with holes drilled for lightness may cause foaming in the gear lube (depending on lube) and also adds tremendous drag on the engine.
6. All quickchange gears are matched sets. Never mix them with a gear from another set.
7. It is recommended that you always use at least 3/8 inch breather line on the top of the rear. Run that line up as far as possible and top it with a good breather filter, like a K&N or the equivalent.
8. About once a month, it is a good idea to remove your rear cover and use a long, flat aluminum file to clean up both edges of the mating surface. This will insure a clean, flat mating surface and guard against leaks.
Pinion Pre-Load 10-15 Inch Lbs. At room Temperature
Total Pre Load 30-40 Inch Lbs. with bearings pressed on
Note: All set up specs are taken from the pinion. To make set up easy, Frankland Racing sells a Trouble Shooter Kit (K). It comes with a pinion adapter, dial indicator, and mounting bracket. When ordering, please specify the model of the rear you have.
Helpful Hints on Set Up
(1) Purchase a set of set up carrier bearings. The bearings are honed so they can slide on and off your differential making your set up time much faster. Part# QC0289.
(2) When setting pre-load and backlash, set up the pre-load first.
(3) Start with an excessive amount of shims on the backlash side (right side) of the differential. This is to prevent a false pre-load reading. A false pre-load reading will occur if there is negative backlash (Negative backlash means that the ring & pinion gears are crushed against each other). Once you have an excessive amount of backlash, continue adding or subtracting shims to the left side of the differential until 30-40 inch lbs. is achieved.
(4) Once the pre-load is set, start setting the backlash by moving shims from the right side to the left side until .010-.013 of backlash is reached.
While the rear is out of the car and taken apart, inspect all seals and bearings for wear.
Torque Specs for Bolts
3/8” Bolts 30 foot lbs.
7/16” bolts 40 foot lbs.
Loaded Pinion Removal
Heat area around the pinion until old pinion unit taps out easily. Never concentrate heat around the pinion nose bearing.
Loaded pinion Installation
Heat the pinion area of the center until loaded pinion drops in easily. Never concentrate heat around the pinion nose bearing.
Use set up bearings to get preload to 25in pounds then press on new bearings. Preload will go up.
If you have any problems please call our tech line (724) 898-2111.