Last month, we covered the history of Jaguar’s ‘classic’ independent rear suspension unit. We now go on to analyse its strengths, weaknesses, interchangeability, and possible modifications…
Final Drive
The most natural place to start is the heart of the unit – the final drive assembly, colloquially known as the ‘diff’ or differential. The good news is that - given maintenance of the correct oil level – these units will cover inter-galactic mileages without failure, albeit developing a little backlash and audible whines along the way.
The downside is that these units are prone to oil leakage via both the pinion and output seals, not helped by being so close to the heat generated by the inboard brakes. The seals were originally leather and then rubber but all are prone to ageing and deterioration. Later neoprene replacements fare rather better and make the occurrence of oil soaked rear discs a rarer occurrence.
These units were supplied by the long established British company, Salisbury (later owned by GKN) and came in three distinct variants. Maybe anticipating potential supply problems, a rare mid ’80s interloper was supplied by the American Dana company as a dual source option. These can be readily identified by the featureless flat bottom of the casting.
All versions comprise a casing that provides location for the lower wishbone pivot carriers and brake calipers – containing a crown wheel and pinion assembly, a differential unit, and removable output shaft assemblies.
Salisbury parts supply is generally excellent, with one or two exceptions: The first version featured shim adjustment of all internal bearings and removable ‘horseshoe’ caliper carrier brackets.
Version two had these brackets incorporated into the output shaft assemblies, with twin row ball, sealed unit bearings looking after output. These are now unavailable - a similar dimension bearing can be obtained for a washing machine drum, but these soon fail when subjected to high suspension loads! All is not lost, as the crush tube adjusted examples from the later third version can be adapted. This last iteration also has crush tube setting for pinion bearing preload and uprated oil seals.
The Dana axle is best avoided due to minimal parts availability, but ironically (see page 14) SNG Barratt has just reintroduced pinion seals after a decade’s non-availability.
Complete assemblies are fully interchangeable across all years of production and ratios can be swapped in a range between 4.55 and 2.88:1. The ‘open’ and ‘Thornton Powr-Lok’ plate type limited slip differential carriers can be incorporated, or for ultimate traction without the understeer-inducing traits of the Powr-Lok, – an aftermarket Quaife geared LSD can be fitted.
With the standard LSD, groaning on cornering suggests the wron
