Swapping Rear Axles & Spring Pads - E-Z Rear Retrofit

Stock is stock, and if you stick with it, practically anything you'll need to do to your Mopar will be a simple bolt-on, repair, or maintenance procedure. Start altering, modifying, and changing things, and fabrication will make the difference between a well-executed modified Mopar and a street machine that "isn't quite there."

So it was with our '71 R/T Charger. While the sheer rarity and collectability of these models means that, today, most are put together as strict restos, this one's been with us for nearly 25 years, rebuilt numerous times, and has always been treated to mild modifications.

"Subtlety" was the watchword for the path taken thus far-from the brake upgrades, to the healthy performance suspension underpinnings, to the six-speed Richmond tranny; nothing to drastically alter the look of the car, but enough to make it perform on the open road like no original R/T could. One of the mods was a set of beautifully restored American Racing Daisy wheels in a wide 15x8.5-inch pattern. While they looked good with the deep-dish we love, the limited backspacing had us less than satisfied with the overall execution.

With 275/60/15 rear meats, the wheel/tires package was offset a little too far outward for our liking. Determined, we weighed the options. This wheel design, like many from the '60s and '70s, was never offered in a more suitable offset, so that option was out. In the '70s, fender flares were the answer, but on our R/T in 2002? Not even if we popped an aneurysm.

The simple solution was to narrow the rear. This can be an expensive proposition, but some interesting swaps are possible with Mopar rears if you know the specs (see chart). A stock E-Body rear is just a bit narrower than the stock late B-Body-just enough, in fact, to hatch a plan. Residing in the back corner of our shop was an 8 3/4 E-Body rear we pilfered from a big-block Challenger at the local serve-yourself boneyard. With a pair of replacement perches and a zap of the welder, it would serve as a mildly narrowed rear in the Charger's chassis. In our case, enough to make the wheel-and-tire combo fit like they belong.

For our purposes, the swap represented only a subtle change in width; although more radically altered, or tubbed, cars can similarly swap rears across body styles for much less than a custom-narrowed rear. Of course, with the more radical changes in axle width, the springs have to be moved inboard as well. Is the swap option always the best way to go? If custom axle shafts will be purchased anyway, narrowing a wider rear to a custom width makes more economic sense since the housing ends and welding are the only additional items involved. If, as in our case, a simple swap will work, it's the cheap and easy way out.

The techniques for replacing the spring pads shown here become necessary if the popular kits for moving the stock leaf springs inboard are used. Mopar performance sells kits for A-, B- and E-Body cars with offset shackles and spring hangers that move the springs inboard 3/4 inches, as well as a more radical kit that moves the springs into the framerail for a 3-inch inward shift. In either case, the spring perches must be relocated to match. Whether swapping rears or just sliding the mounting pads over to relocate the springs, careful measurement and a little welding is all it takes.

Basic Rear Axle Dimensions
Common Mopar Rears