Rear Tyre Wear On My 319 Sports

Over the past few years I have noticed excessive tyre wear on the rear of my 319 Sports.  I was only getting 5 - 6,000 miles of life; I suspected a bent axle case.  After checking the positions of the axle and springs, which were OK, I examined the driver’s side half shaft which I had replaced 3 years ago.  The original shaft had 3 broken splines which I had put down to wear and tear.  The replacement shaft had suffered the same fate.  This confirmed that the rear axle was bent, putting the bearing housing out of true with the diff carrier and putting excessive load on the splines.  After taking a good look at the bare axle casing I made the decision to replace the case.  Now finding one may be easier said than done.  

The 319 Sports rear axle is 50mm narrower than all other 319 models.  Luckily, I had a spare standard 319 axle which I would have to modify by reducing the track by 50mm.  This modification was undertaken by making a set of jigs and fixtures to enable me to shorten each side of the axle casing by 25mm using the fixture to hold each bearing housing in the correct position i.e. in line with the central diff carrier to allow it to be rewelded in exactly the correct position.

First, I made two dummy bearings with the same OD as the half shaft wheel bearings which normally support the differential.  These were made with 50mm bore to take a 50mm mandrel.  Luckily, I had a spare diff carrier which I used to support the centre of the mandrel.

As shown in the drawing, 25mm was removed from the side of each axle case.  The best place to cut the axle was to the inside edge of the axle spring support plate.  The area to be welded was V'd out – as shown in the drawing (A).  The new axle cases were assembled with the mandrel and dummy bearings clamped together and rewelded.  During the welding process it was very important not to distort the position of the components.  A number of good tack welds were placed around the casing.  To prevent any possible distortion 12mm welds were placed equally around the axle case until the welds joined up.  The rework of redundant 319 axle cases solved the problem.

Norman Mascall.