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Chevelle Tech Talk May '03

Dick Brandt Mar 13, 2003

This month we are going to talk about rearends and mounting hardware. From the factory, the '64 Chevelle was delivered with the 10-bolt (the number of bolts holding on the rear cover), Spicer-style differential. The 10-bolt was standard from 1964 to 1972. If a beefier rearend was needed, the 12-bolt was used as an option from 1965 to 1972. All 10-bolts used an 8.2-inch-diameter ring gear while 12-bolts were 8.875-inches.

All Chevelles through 1972 had their rearends mounted in the frames using a four-link trailing arm setup. As for springs, from 1964 to 1966, all Chevelle and El Camino rearends used a flat coil mount pad and an oval bracket that bolts to the pad, holding the coil in place. From 1967 to 1972, GM changed the coil mount to a conical type, in which the coil rides on a small cone without any type of attaching hardware. Also, the '68 to '72 rearends were 1-inch wider from drum to drum. From 1965 to 1972, all trailing arm and rearend mount bushings were the same. However, in 1964 a small bushing was used on the top ears of the rearend. The next year, GM used extra strengthening ribs on the center section of the housing. These ribs were on the top of where the axle tube slides in and lead up towards the top of the housing. This would also be the same as the 12-bolt used in the extremely rare '65 Z16 Malibu SS.

Twelve-bolt rearends have become difficult to find. Fortunately, there are companies that can repair an existing housing or build a new one. Originally, the axle tubes were pressed into the center and were tack-welded in place. It's smart to have the housings checked for straightness and have the tubes fully welded. Additionally, if you're getting a new rearend, you can have any gear combination, new Eaton Posi units, and forged axles installed. These new assemblies beat fighting the old, seized-up junkyard rearends that have seen 30-plus years of hard service. You can also have these rearends narrowed for added clearance on your street cruiser or for the 22-inch slicks under your Pro Streeter.

Removing or installing the rearend in your Chevelle is fairly straightforward. The safe way to do it is with two people: one manning the floor jack, the other steadying the rearend. The vehicle should be supported by a pair of jackstands on the frame, and the rearend should be supported by the floor jack. Start by unbolting the shocks from the rearend using an 11/16-inch wrench. Next, remove the brake flex hose near the center of the frame. It is usually easiest to disconnect the hose from the front-to-rear hard line and leave the hose and axle lines with the rearend. You'll also need to remove the single parking brake cable that links to the pedal and release the two separate cables from their frame mounts before the rearend can be removed.

Once those tasks are complete, lower the rearend so you can reach the four mounting bolts that attach the trailing arms. A 3/4-inch box-end wrench and a ratchet with a 3/4-inch socket work best. If you're working on a '64-66, now would also be a good time to remove the coil mount bracket.

When it comes to sliding the bolts out of the trailing arms, raise or lower the floor jack to get the rearend at the height where tension on the bolt is minimal, then tap them out with a hammer and punch. Once the bolts are out, the housing is free, so be careful lowering it to the ground. The installation is the reverse of this procedure. In the next issue, we will continue under the car and discuss the trailing arms and rear disc brake kits.


To contact the author, please call or write him at:
True Connections
3848 Pierce St., Dept. SC
Riverside, CA 92503
(800) 600-4144

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