No Fear Gears

All too often the average enthusiast installs a killer engine into his Chevy only to find that the car doesn't accelerate like it should. He then realizes that the factory 2.73 rearend gears are holding the engine back. Whether your vehicle is meant for drag racing or top speed cruising, it's crucial to have the proper rear gear.

The plan here was to upgrade the 10-bolt in our pal Larry Richard's 175-mph '87 Monte Carlo. His 7.5-inch 10-bolt carried a 3.73 gear ratio, but it needed a new posi, bearings, and axles. The 3.73 gear ratio combined with Richard's six-speed transmission allows the 355ci 500hp engine to make use of every last bit of horsepower when he's well into triple-digit speeds. To get the project done, we contacted Drivetrain Direct in Corona, California. Drivetrain Direct supplied its rearend-rebuild kit and a pair of Superior axles. The kit includes a Superior ring-and-pinion, Timken bearings, an Eaton posi, and all the necessary shims and gaskets. The company also lent us its head mechanic, Martin Barraza, who showed us how to properly rebuild the rearend.

Remove the rearend cover and drain the 3 quarts of gear oil. Next, extract the cross-shaft bolt (A) and cross-shaft (B). Then, spin the rearend until the ends of the axles are visible inside the carrier. Locate the axle C-clips and remove them by pushing the axles in toward the center to free them. Once the axles have been removed, you can unbolt the main caps and remove the carrier.	It's always a good idea to replace the axle bearings located in the ends of the axletubes. Hundreds of repetitious heat cycles have a tendency to really seat these bearings. If they have been in the rearend for a long time, you are going to need a slide hammer to remove them.	Before we could clean the housing, we had to remove the pinion. We removed the 1-1/4-inch hex pinion nut and drove the pinion assembly out with a brass punch and a hammer. From left to right you can see the yoke, seal, outer bearing, crush sleeve, inner bearing, depth shim, and the pinion gear. Once everything is out of the way you can remove the pinion races with a punch and hammer.
Before attempting to remove the ring gear from the carrier, be aware that these bolts feature a left-hand thread. When re-installing your new ring gear, it is best to use new bolts and torque them in a cross-tightening pattern to 75 lb-ft.	The carrier bearings must be pressed onto the carrier. This requires the proper tools to remove and replace them and it's best left to a professional shop.	The holes in the rearend housing allow gear oil to lubricate the axle bearings. It's crucial that the rearend cover gasket is equipped with these openings.
The next step is to install the pinion races and pinion. Generally, the stock pinion depth shim (located between the pinion bearing and the pinion head) will be the correct thickness and can be reused with the new components. When assembling the pinion into place, include the crush sleeve between the two pinion bearings. This sleeve must be replaced every time the pinion nut is torqued. Many mechanics use an impact gun while others insist the nut should be torqued by hand. Either way, the nut should be tightened to produce 24-32-in-lb of torque to turn the pinion gear with a new bearing. This is without the ring gear in place.	We are now ready to install the complete carrier into the rearend housing. Carrier shims are placed between the carrier bearings and the rearend housing on both sides. These shims place a pre-load on the carrier and keep pressure against the bearings. The shim thickness on both sides also determines the amount of ring-gear backlash. Backlash is adjusted by changing the shim thickness side for side. To decrease backlash, increase the thickness on the left side while reducing the thickness an equal amount on the right side. To increase backlash, do the opposite. Once the carrier is in place, re-torque the main caps to 65 lb-ft. At this point the carrier should turn freely inside the rearend housing.	With your new carrier installed, apply the provided marking compound to five teeth of the ring gear then spin the carrier (while applying a light load on the gears) until it makes several revolutions.
According to the pattern imprinted on the ring gear, a trained professional can determine whether the right number of shims have been installed.	The key to a proper rearend setup is to establish the correct pattern. This comes from following the factory specs. Backlash is the amount of clearance between the ring-and-pinion teeth. By placing a dial indicator on a ring-gear tooth and rocking the ring gear back and fourth, this rearend showed an acceptable amount of backlash between 0.005 and 0.009 inch. Pinion depth is determined according to the thickness of the pinion shim installed between the pinion gear and the bearing. A proper pinion depth setting is noticeable once the marking compound is applied. Increasing the thickness of the pinion shim places the pinion gear closer (deeper) to the ring gear.	Once the carrier is properly placed inside the rearend housing, reinstall the axles, C-clips, cross-shaft, cross-shaft bolt, and rearend cover. Because we installed a posi-traction unit, 3 quarts of limited-slip gear oil were used instead of the standard rearend gear oil.