Edited on 2015-02-06 9:50:35
I could not find anyone locally who could rebuild my old unit (leaking, clunking noises in reverse, whining), so I figured that a replacement might be a better option.
I relied upon a local Jag shop that has some dismantled cars, and he said that the '85 XJS diff would work. My replacement differential ($650) was from a 1985 XJS (VIN SAJNV5846FC122964 ~52,000miles) with tag ÔÇ£43:15 / 2.87ÔÇØ. It has no drain plug on the flat bottom of the housing, only a fill plug on the rear cover, and the input flange is ÔÇ£squareÔÇØ type as opposed to ÔÇ£roundÔÇØ type on Salisbury. Therefore, it must be the DANA.
The '85 2.87:1 was an exact fit. I used my original brake calipers and discs since the ones on the '85 were badly corroded. But I remember not having to reuse a couple of the caliper mounting brackets from the older diff since the newer diff has them molded in. Otherwise, all dimensions were a perfect fit. It sure makes for a more leisurely engine speed on the highway, and now 1st gear is much more usable at low speeds around town.
But now I have to get my speedo recalibrated. In the meantime I can drive using a windshield mounted GPS.
BTW, the tag ÔÇ£43:15ÔÇØ calculates to 2.87:1 (i.e. 43/15=2.87), but Jaguar always refers to it as a 2.88:1. Go figure. Anyway, my service manual also shows that non-USA Series II E-type 2+2 automatics used 2.88:1 ratios, so keep that in mind if it helps to locate a replacement diff.
There are excellent discussions about the later differentials at Coventry West http://www.coventrywest.com/jaguar-tech-tip-12 and Jag Lovers http://www.jag-lovers.org/books/old-xj-s/finaldrive.htm
Good luck!