Way back in pre history, when I was a kid, I had a 1955 Plymouth that I had swapped a 413 cuin Dodge engine into. It only took one press of the accelerator, to shear the stock axle keys.

Not wanting to repeat history, I decided to use the ever popular Ford 9″ to replace the stock Dodge axle. As luck would have it, a good friend had picked up a 9″ from a shop that builds Cobra kits. The rear axle was from a 1967 390 Mercury Cougar. The flange to flange width was the same as the Dodge and the pinion offset was close to being the same as the Dodge as well.

Ford 9″ Rear Axle

I used my fabrication table and a couple of jack stands to support the Dodge axle while I removed it and the rear springs. Before pulling the plug on the Dodge I measured the pinion angle for reference when I install the new spring perches on the Ford axle.

The rear suspension on the Dodge had a really neat design feature. The rear springs are not parallel. The rear spring shackles are centered on the frame, the front spring shackles are mounted to the inside of the frame, which helps to trianglulate the rear end to reduce sway while cornering. In 2006 Toyota announced a similar design in the new Tundra pickups and touted how much it improved handling. Oh well, nothing is ever really new is it?

I replaced the Dodge axle on the fab table with the Ford and rolled it under the rear of the wagon where I had already replaced the springs. I then lowered the wagon using the lift until I could position the spring perches and tack them in. After checking dimensions and alignment, I raised the lift and moved the table behind the car where I completed welding the spring perches to the axle. To minimize warpage, I used the same stitch welding technique that I had used on the frame in the front.

One small note … while I had the axle supported with the jack stands I also supported the pinion with a third stand so that I could rotate the housing as I welded the perches. While I was moving things around, I happened to jostle the axle on the jack stands and knocked one over, my reflexes took over and I tried to catch the pinon to try and stop the fall. Not a good plan… The pinon pinned my left hand to the heavy steel table top and had my neighbor and good friend not been there to help lift the axle up, I could have been there for quite a while! Anyway, a short trip to the emergency room, 6 stiches later I was back in the shop mopping up the blood. I was very lucky that the pinon missed all the bones in my hand and only cut the fleshy part of my hand between the thumb and forefinger.