Allard Quick Change Differential

By David Hooper

In 1952, the Allard Motor Company offered a modified dead axle assembly for the J2X complete with removable center section to allow the Halibrand quick change differential to be easily retrofitted to the USA cars. Due to high import costs, it was not cost effective to import quick change differentials from the USA. However, due to interest from existing Allard owners plus HWM, it was decided to make an Allard version.

The Allard quick change differential was produced in 1952-3, with at least 15 units being manufactured on site and by Jack Knight Engineering. The design was based on the Halibrand unit, however we were unable to find a UK foundry that was able to cast steel inserts for the bearings in a process similar to the steel liners bonded into the Alfin type brake drum.  Without these inserts the pinion bearing housing was achieved by a machined insert which bolted onto aluminum casting.  The standard Ford based side steel covers were replaced by Aluminum castings. 
We supplied a number of these axles to HWM and Coopers for use in their larger sports cars - the Wick brothers had one fitted to their front engined Cooper-Jaguar.  Unfortunately, the units were not very reliable due to manufacturing compromises that were required. An updated version was made replacing the counter shaft composite front bearing with a standard ball race, and this model is the differential unit fitted to the Chrysler dragster and Steyr sports car. After the Clapham High Street fire, a number of un-machined castings were rescued from the ashes, which are no doubt gathering dust somewhere. Unfortunately only a couple of complete units are known to exist today.

Note: HWM replaced the “Allard” labeled housing plate with one labeled “HWM.” This has caused some to believe that HWM manufactured the differentials, when in fact they were made by Allard.