Rearend Maintenance - Rear Gear Checkup

As long as the pinion gear and its bearing look good, it can be reused. If that is the case, not removing the shims and crush sleeve should ensure the pinion depth will still be correct. Of course, don't forget to check the bearing race inside the front cover. It should be free of scratches, gouges and heat marks.

Don't forget that even if you use an oil pump to cool and move lubricant around in your rearend, it doesn't work until the car starts moving. Protect the bearings with a liberal coating of white lithium grease.

They may be more expensive, but Cook recommends using a quality Viton pinion seal to minimize leaks.

The internal oil pump is actually driven off of the pinion gear. It requires a special pinion with a hex cut into the end of it, and the pump's driveshaft slots into the end of it. Cook says he purchases his pumps and pinions from G-Force South in Asheboro, N.C.

Be careful when installing the spanner nuts so that they do not get cross threaded in the housing.

Cook says he tightens the spanner nuts while turning the ring gear until he starts to feel some drag and then backs off a bit, which should at least get you close to the correct backlash. After that, you can use the spanner nuts to move the carrier laterally to increase or decrease backlash.

Backlash should be checked in at least four places around the ring gear with a dial indicator. With the pinion gear held steady, you should have between 0.008 and 0.010 of play in the ring gear. If your backlash changes signifi cantly at different parts of the ring gear, that's a sign that the ring gear isn't seated snugly to the carrier all the way around.

Once your backlash is correct, paint a section of teeth with gear paint and spin the gears several times to check the pattern. Use a rag and squeeze the pinion shaft while spinning the ring gear to provide some resistance-this will provide a more accurate pattern.

Cook finishes assembly of the oil pump. He says that unless trash somehow gets into the system he rarely sees any real wear in these types of pumps.

The last step before buttoning everything up is to wire-tie the bolts. This is definitely a step not to be overlooked because once the center section is installed in the rearend, it's impossible to check and make sure vibrations haven't caused the bolts to loosen.

Your pattern should show the gears mesh on the bottom portion of the ring gear teeth. This is different from a passenger car where you would normally want the pattern to be centered, but in a high-horsepower racecar, the extra horsepower will push the pattern toward the center in real-world use.