Rear Axle Modifications - Axle-Chop How-To

One word of caution is that a small percentage of Mopar 8 1/4 axleshafts (as well as some Fords) feature extralong 4-inch undercuts (pen points). Unless you are building a supernarrow Pro Street- or dragster-style axle, there isn't enough material diameter at the ends to allow resplining. Our A100 axles (top) have 3-inch undercuts; no problem with our 3-inch chop job.

Next, the axles are chucked up in Sutton's Goodway lathe. In three steps, Ed removes 0.038 inch to achieve a constant diameter for successful resplining.

The pen points out the 0.187-inch-deep factory surface hardening that is only mildly affected by the 0.040-inch-deep spline cuts (right). There is still plenty of strength left for all but the most serious horsepower levels. Again, the Suttons say this operation is safe for 3,400-pound cars running 11.0 seconds with an automatic or 12.0 seconds with more brutal stickshifts.

As for you GM guys, the constant-taper shaft design of virtually every passenger-car axle type from the '55 Chevy to the classic 12-bolt cannot be resplined. Fingers point to where diameter reduces from 1.400 to 1.270 inches. Your only choice is custom-length aftermarket replacement axles to suit your narrowed housing.

The pen points to the gradual radius Ed puts into the transition from the freshly machined and nonmachined axle surfaces. This eliminates the stress riser and potential failure point a sheer 90-degree merge would create.

Do the Suttons know axles? Here's a small selection of the over 30,000 ring-and-pinion installations they've performed since opening their shop in 1980. They sell the used-up stuff shown here to the local scrap man, who loves the high-grade metal.

After careful measurement, the chop saw removes 3 inches from the end of each axle. Make sure they're resting flat on the saw table before cutting to get straight cuts.

The vertical mill cuts one 0.040-inch-deep spline at a time using a specially designed cutting tool that spins at high rpm. A dividing head on the mill precisely controls the length and depth of each cut and in this case delivers the stock Chrysler 30-spline axle end specification.