Project Austin ‘Special’: Rear Suspension Upgrade

It has been a while since I have shared some progress on the Austin ‘Special’ so I figured it was time for an update. In the last installment I divulged what I planned to do in order to upgrade the Austin’s mechanical running gear. This time around we will dive into the rear suspension.

MG B rear axle

As previously noted the rear axle is going to be a MG B unit which is stronger with much better replacement parts availability. It also is, crucially, the correct and quite narrow width. Both the MG  B and Austin A40 are equipped with leaf springs and lever shocks. I did want to change from the lever shocks to some more common and up to date gas shocks as the Austin shocks were completely worn out and I did not receive any MG ones with my axle. I did have a set of MG B leaf springs however.


Here is the Austin axle out after a brief (ok, not that brief) fight. I made good use of these wheel sliders to move around axles. I had a dream that this might be close to a bolt on operation but some further measurements showed I had no such luck as the spring perches were just a little off.

Austin (top) versus MG B (bottom) spring.

The Austin springs looked like a better candidate and cleaned up nicely. A fresh coat of paint made them look respectable.

I ordered new bushings for the springs. Luckily these were not too crazy of price like some of the A40 replacement parts.

A test fit confirmed that the spring perches were off just a touch.

And so the perches had to be cut off.

For new perches a set of trailer ones lightly modified worked. I would just need to attach the shock mount to them later. I lost count of how many times I had the axle in and out but on this attempt I am confirming the location of the spring perches before tack welding on followed by yet another test fit.

Looking through specifications for shocks I came up with these for a 1987 Dodge Colt Visa wagon. They had an extended length of 15.55″, compressed length of 10.75″ and a stroke of 4.8″. The donor vehicle is likely in the same weight ballpark as well so I figured they should work well. Additionally, the two mounting ends looked easy to work with and fabricate mounts for unlike some other options.

This is my lower shock mount tacked on. It does not look like much but a few manufacturers used a similar method and it should be plenty strong. I later realized the bolt portion was too short once I did the final welding so I got to do this step twice.

I tacked welded a couple of tabs to the frame for the top shock mount then waited to separate the chassis from the body for final welding. As you may recall the car was no longer bolted to the chassis when I bought it so I got to skip that step. Removal was complicated by the transmission being seized to the engine which meant it had to come out with the chassis as the two together would not clear the hood opening. The head came off the engine to gain some clearance. The front body work will likely come off when the much taller and larger Toyota 20R engine is slide in but for now its remains loosely bolted together so I do not have to find a place to store it.

There is a video of the process if you are interested. The audio is lousy as usual but basically the process was to jack up the body while dropping the frame. The frame pulled out the front just clearing the head bolts. Unconventional perhaps but it allowed me to do it solo. As a bonus I have a nice collection of jack stands now.

Once clear of the body it was much easier to finalize the welding of the top shock mounts as well as mock up the rear suspension. I still need to press out the old spring bushings (or just the remains), press in the new ones and get a few bolts for the U-bolts holding the axle to the spring but the major bits are complete. I also sold (very cheaply) my Austin axle to a guy building a T-bucket roadster so it will live on a while longer. Next steps are pulling the stock engine, and mounting the front suspension.

Project Austin Special Series:

Project Austin ‘Special’: Acquisition of a 1952 Austin A40 Somerset

Project Austin ‘Special’: Assessment of the Car

Project Austin ‘Special’: Four Becomes Two

Project Austin ‘Special’: Planned Mechanical Upgrades

Project Austin ‘Special’: Rear Suspension Upgrade