Removing the Differential Bearings

I finally got round to rebuilding the Ruby rear axle, and decided that the thrust ballraces that flank the differential would have to be replaced.  The problem was how do you remove them, for they are pressed on close to the diff. casing and using a puller only removes the outer part of the race, causing the balls to spray out in all directions over the floor, and leaving the inner race stuck fast on the housing.  Attacking the inner race with a cold chisel would only damage the diff. housing, and cause problems for the fitting of the replacement crownwheel.  I consulted 'The Austin Seven Manual' by Doug Woodrow for learned advice as to the correct procedure, but was dismayed to find that no reference was made  to this item whatsoever.  

Some considerable time later, I stumbled upon a chance remark in an article in the 'Austin Seven Companion'. It was part of an article by the late, and much respected, Jack French, and is a mere two lines at the top of page 169 stating ‘The angular contact races on the diff carrier are removable by using a pin punch (trade name for a wire nail) through holes provided in the carrier’.  So there is was – it had to be a simple solution, but that one was far from obvious.  

The following images show how easy it was to do, once I had borrowed a 3/16” dia pin punch.  A wire nail is quite definitely not up to the job!.  It is essential to support the casing halves to protect the bronze bushes that carry the half shafts – I turned up a suitable piece of brass bar to provide the necessary support mandrel, and a bit of work with a large hammer produced the desired result.

Diff bearing 1



The carrier halves showing the holes for inserting the punch.






Diff bearing 2




Punching the bearing. Note the brass mandrel to support the shoulders of the carrier.








Diff bearing 3



Bearing removed , with more mandrel detail.







Diff bearing 4



Heating the new bearing in an oil bath.







Diff bearing 5



The refitted bearings.







I employed my favourite method of heating the new thrust bearings to 180 deg.C in a bath of oil, using a camping stove and a digital thermometer. At that temperature, the bearings simply slip over the shoulders of the diff. carrier and seat down correctly without further pressing/hammering. It’s important to make sure you’ve fitted them the right way round though!


This article, written by Bob Kneale, appeared in CA7C Seven Focus in Oct 2015 pp 22-24.