 Use a floorjack to lift the...  Use a floorjack to lift the rear of the car off the ground, and position jackstands under the car frame just ahead of the front springboxes. Remove the rear lug nuts (breaker bar and usually a 3/4- or 13/16-inch socket) and remove the rear tires. Slide off the rear brake drums, which may require backing off the brake shoes if the brakes are worn. |
 Use a ratchet, usually with...  Use a ratchet, usually with a 9/16-inch socket and 2-inch extension, to remove the four or five axle-bearing-retainer nuts. Accessing the nuts requires aligning the factory-drilled hole in the axle with the nut to be removed. Some aftermarket axles don't have an access hole so you'll have to use an open-end wrench. |
 With the axle-bearing retainer...  With the axle-bearing retainer plate loose, slide out the axles. In some instances, the axles will be a tight fit in the rearend housing; you can pull them out by installing the brake drum backward and threading on a few lug nuts using the drum as a slide hammer. Don't be too surprised if gear oil pukes out the axle housing. |
 When removing the axles, dont...  When removing the axles, dont damage the axle seal in the end of the housing; remove the axle all the way rather than letting it rest on the seal. Note the position of the retainer plate gasket, axleshafts, and shims so they can go back where they came from. Inspect the axleshafts, bearings, and seals for damage that may need repair. |
 Remove the four U-joint strap...  Remove the four U-joint strap bolts using an end wrench (usually 7/16 or 3/8), then remove the driveshaft. Remove eight of the ten rearend centersection nuts (using a ratchet with 9/16-inch socket) and loosen the two remaining bolts, but do not remove them. Position a drain pan under the rearend and use a screwdriver to seperate the centersection from the rearend housing, allowing the gear oil to drain out. Pew! |
 Remove the last two nuts and...  Remove the last two nuts and then pull out the centersection. It's heavy, so you may want to position a floor jack under the centersection to hold its weight and then lower it using the jack. |
 Reach into the rearend housing...  Reach into the rearend housing to feel for shavings, dirt, cracks, or wear. Use your fingers to slosh the remaining gear lube into the drain pan. |
 If your new rearend centersection...  If your new rearend centersection does not have a factory pinion snubber (if applicable) attached to it, reuse the snubber assembly from the old centersection. |
 Use a gasket scraper, brake...  Use a gasket scraper, brake cleaner, and a rag to clean off the centersection-to-housing mating surface. You can install the new centersection and seal it with only RTV, but using a gasket is better. For an 8 3/4 rear, Mr. Gasket makes a gasket under PN 81. |
 Carefully install the new...  Carefully install the new centersection into the rearend housing so that it properly aligns on the 10 mounting studs. |
 Thread on the 10 centersection...  Thread on the 10 centersection retainer nuts and then use a torque wrench to tighten the nuts to 45 lb-ft. Rotate the pinion gear by hand to ensure no binding or interference occurs. |
 Reinstall the axles being...  Reinstall the axles being careful not to gouge the axle bearings and/or axle bearing seals. Year One has new foam axle gaskets if you want 'em. Thread on the axle bearing retainer plate nuts. |
 Use a torque wrench to tighten...  Use a torque wrench to tighten the axle bearing retainer plate nuts to 35 lb-ft, making sure the axle doesn't bind as you tighten. |
 Most Mopar 8 3/4-inch rearends...  Most Mopar 8 3/4-inch rearends have an axle adjuster on the passenger-side axleshaft. After the axles are in, there should be about 0.008- to 0.018-inch endplay or problems may result. To adjust endplay, rotate the notched adjuster ring. On rearends so equipped (such as a Mopar 8 3/4) be sure to reinstall the endplay adjuster ring retainer clip that mounts using one of the axle bearing retaining plate nuts. On rearends without an adjuster ring, axle endplay can be adjusted using different thickness gaskets/shims. |
 Install the proper amount...  Install the proper amount of rearend gear lube using the fill hole in the side of the centersection. Most of the Mopar 8 3/4-inch rearends require about 2 1/2 to 3 quarts of lube. Or, just fill it until oil drools out of the fill hole and youll usually be close enough. |
 Before bolting up the driveshaft,...  Before bolting up the driveshaft, make sure you have the right yoke, as two different U-joint sizes were used on the cars that came with 8 3/4 axles. The spline count affects yoke interchangeability, and so does the pinion type; changing yokes on the 489-casting-number case is difficult to do properly because they set pinion depth with a crush sleeve that can be damaged if you over-tighten the pinion nut. |
 After youre done, rotate...  After youre done, rotate the pinion gear to ensure proper rearend operation. If its OK, reinstall the driveshaft. Afterward, reinstall the brake drums and rear tires. Remove the jackstands from the car and then road test it to verify proper operation. Switching from the stock gears to 4.30:1 gears made our Duster a real street/strip warriorwe were really diggin its new launching prowess. |
In the Nov. 1998 CC you read about a real-world street machine buildup using a 1970 Duster. As part of the story, we shoehorned in a stout 360 V-8 and an 8 3/4 rearend. The rear came with an open diff and 3.23:1 gears, but we perused the classifieds and found a rearend pig loaded with a limited-slip (Sure-Grip) differential and steep 4.30:1 gears. Installing a new centersection in a Mopar 8:3/4 rear, Ford 8- or 9-inch rear, or early-style (1955-1964) GM 10-bolt is easy--the job is similar for all those diffs--and it can be done in an afternoon. There are a few special tools and tricks to properly performing the work, and thats exactly what this story is about--showing you whats really needed to do a swap.