Geoff Lowe
<geoff.lowe@survey-inspection.com>

SB1946
UK

If you would like to ask any questions or require any help to do these jobs on you own car please drop me an e-mail at: Geoff.Lowe@survey-inspection.com

5 Link Rear Axle Modification

Since doing the diff modification back in March 07 the car has covered about 2,500 miles and there is not a hint of oil leakage, it has been 100% success. So I am now putting a 5 link system onto the axle but not modifying the car's chassis or body work.

I started by removing the axle and getting it on the workbench. Now I am not in a fully equipped workshop -- I am in my garage with only limited equipment and a good imagination. I acquired some 2" x 1" box section from which I cut two 5½" long segments. I radiused one end of each piece to fit the dia of the axle ends.

Next I got a long rod of ½" dia to slide through the A frame bracket. Cutting two pieces of wood to hold the rod parallel to the axle, I could then work out where to drill the box section. This worked out at   4¼"   from the bottom of the radius.

The box section was drilled ½" clearance dia and then the rose joint was placed on the top and scribed round so I could now cut the box section to length and cut one edge out about 1½"up to allow the rose joint to move in order to let the axle move up and down when in position.

Box sections ready for welding

Now for the welding
With the rod still through the diff bracket I put the box section on each end and positioned each box at the ends of the axle just where the cast axle end comes to just leaving room for a weld, (if you are doing this on a Ford axle you would have to work it out as the Ford axles are a bit longer) before welding check that the rod is still parallel to the axle and looks square to the eye. Tack weld them on and check alignment again, if all is ok weld them on. I used an arc welding set and did a bit on one end and then the other just to keep the heat down.

Once these had been welded in position I gave it a coat of paint and then it was ready to go back in the car.

The rod lining the brackets up

A welded bracket
(note welded up grease nipple hole)

I put the axle back in but did not fit the springs and shocks so when I make the bottom arms I can check that the axle has full movement up and down without it binding or stressing any parts. This all worked very well as the new bottom radius move in the same plane as the A frame.

Note the missing shock

Note the jack moving the axle up and down

Making the bottom radius arms
With the axle back in the car with the A frame and top radius arms connected I could now get the length required for the bottom radius arms. These have a ½" rose joint on one end and the same rubber bush as the A frame on the other end. The final length can be adjusted on the rose joint so critical length in manufacture is not to important within a Nat's whisker. I cut my tubes at 8 5/8". When it came to welding the rods together I used gas and braze as the tubes were galvanized and you can't weld galv, I started by brazing the nut to the tube, then fitted the rose joint then fitted it to the car. The other end, in order to get any angles correct, the bush end needs tacking to the tube on the car so an old bush is required. Fit the old bush into its housing and fit to the car using a 5" bolt through the new bush the chassis and the A frame then adjust the rod so it is pressing on the bush housing. Do this on both sides before tacking it up, with using gas and braze this totally destroys the old bush but you should have it tacked in position before the rubber lets go. Mark them so you know which side they are off, remove them from the car and weld them up, fit the new bushes and replace back on the car.

Now with a bit of luck the axle will still travel up and down without any tight spots, and if everything is ok you can refit the shocks and springs, a bit of a headache taking the u bolts back off but for piece of mind that it all works, it is worth it.

The bits

Two lower radius arms ready to fit

Summing up
This job is a bit time consuming but not difficult, if you think each step through before starting each stage and keep checking what you have done before moving to the next step. One of the most important checks is that the brackets that weld to the axle have sufficient clearance between the rose joint bolt head and the chassis I have about 3/8" each side between the head of the bolt and the chassis.

Good luck! Geoff SB1946 back to Geoff Lowe's page