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Instructions for disassembly and assembly |
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Before undertaking any major work on the back axle, it is advisable to check the trueness of the back-axle housing by checking for toe-in/out and camber. Stock specs. are 0" for both the toe and camber, although some race-applications seek negative-camber settings. It is also good to look for fatigue cracks around the center of the housing, at the back cover all the way under, and into the hole in which the differential assembly fits. Look closely as you may have a crack that has been temporarily patched, possibly using body-putty and paint. With the car on the ground and in gear, loosen the axle nuts and wheel lug nuts. Raise and support the car. Once the rear wheels and brake drums have been removed, disconnect the brake fluid lines and contain the fluid. Disconnect the hand brake cables at the wheel-cylinder levers. Drain the differential oil, and while you are under the axle, disconnect the prop-shaft flange from the differential. Remove the brake shoes, making certain of the placement and order of the springs, shoes, and adjustment wedges. Remove the four 5/16" bolts (1/2" head) that hold the backing-plates to the differential housing from both the left and right sides of the axle housing. You should now be able to tug the axle out of the tube, using the back-plate as a handle. A slide-hammer may be helpful for this pulling operation or the brake drum can be reversed, re-bolted loosley and pulled by hand. With the axle, hub, braking, and back-plate pulled out as an assembly, you are now ready to remove the hub from the axle. A special and very strong puller is necessary for the proper removal of the hub to reduce the possibility of damage to the axle and/or hub. Refrain from using heat, a 2-, 3-, or 4-armed puller, or a common press for this task, as damage will likely result unless the taper fit was already loose. The removal of the differential now simply involves removing the 8 bolts (1/2" head, usually) and allowing the 3rd member to be moved forward out of the housing. This is a good time to inspect the housing for fatigue and cracking. The years of stress on the threads holding the differential in the housing likely have pulled the threads towards the mating surface. They ought to be lowered by filing. Use a file long enough to cross the differential hole to support the file and maintain a flat surface. Look closely at the bottom-most bolt hole and surface around it. Cracks form in this area and can travel all the way up the back side of the housing! I recommend bracing the housing using square or rectangular tubing, depending on the horsepower needs. I shy away from the comon "steel-plate" ledge welded across the back side of the tubes. The rear drive-shaft (prop-shaft) flange must be changed to fit the new, larger differential flange. The universal joint size is retained. Use high-grade bolts with a solid shoulder that extends past the joining surface of the flanges and torque to 24 foot-pounds. High-grade bolts (#33) and hardened washers (#35) must be used to join the differential to the housing torquing to 18 foot-pounds. Use sealant around the three lowest bolts to stop oil seepage. Apply a thin coat of Hylomar to both sides of the differential gasket. Gently install the differential assembly into the axle housing as the gasket is easily torn. The oil slinger and the outer seal plate (#42 and #40 on the rear axle illustration) must have its center enlarged to fit the replacement hub. A tapered-ream works well for this. Replace the outer seal (#39) with the larger seal provided. I may have provided the seal-plate. I've chosen a double-sealed bearing at the outer axle rendering the inner seal (#37) less necessary. I'd suggest leaving this seal in place as it does slow the oil sloshing by abrupt left or right turns. The bearings will no longer require lubricating, so don't use the fittings (#4) for greasing. WITH THE AID OF A PRESS (or hammer and a pipe about 10" long and just a bit larger I.D. than the axle) drive the new bearing to its raised boss. The axle is set into the housing, splines meshed and with a soft-faced mallet, driven in until the bearing is flush w/ the backing plate flange. The gasket follows having a thin coat of silicone on both sides and then the seal in its plate (#40) followed by the backing plate. The backing plate is not shown or numbered on the axle picture. Make certain its right-way around and the correct one. The slinger is last ( #42) and the whole jumble can be aligned using two of the 5/16th bolts and without harming the gasket, bolt the works to the housing using the original four bolts. Install the brakes now, adjusters, shoes, wheel cylinder, springs and their retainers. I have marked the hub and mated axle in pairs so make certain the pair is together. I recommend using "WD-40" for a lubricant on the axle's taper and hub's cone and seat the provided square-key up to the 'peened' stops on the axle keyways. After the brakes are installed the hub can be eased in place Use the thicker-hardened washer provided under the axle nut tightening it to about 50 foot-pounds. Fill the differential with the appropriate gear oil ('amzoil' or other synthetic is good). Bleed the brake system and adjust the brakes. Once the car is back on the ground the axle-nut torque can be brought up to 75' lbs. After driving the car GENTLY the axle nuts can be brought up to 110' lbs. Now the car can be driven harder, raised and left to cool before checking the torque on ALL the bolts you just dealt with. Re-adjust the brakes for the final time, lower the car and drive it with joyful abandon.
CHRIS BEEBE. |
Cars - History - Legend - Stories - For Sale