2.88:1 Ratio Dimension Data required

E-Type
21

Thanks all for your replies, but unfortunately, none of that information has progressed my dilemma.

I probably have a better measuring facility than most, is not all, differential repair services, in that I have a Coordinate Measuring Machine (CMM), with a measuring increment of 0.0001mm (0.00000394"), housed in a temperature controlled room.

The measurement was taken by setting the differential housing vertically on the granite table of the CMM, sitting on a parallel faced, hollow boss to clear the end of the pinion shaft, with the boss locating on the machined step for the Pinion Seal. The top face, where the rear cover interfaces was checked for being parallel with the table; it checked out to be parallel within a small tolerance.

As an added step to ensure that any out of square with the table didn’t introduce any measuring error, small as it may be, three points on all four faces that represent the centre line of the Crown Wheel were probed and the CMM aligned via its software to be on the same plane as the four faces. A measurement was then taken down to the ground face of the Pinion Shaft end. Accordingly, my measurement of 72.63 is very accurate.

The only “B” dimension that would work with my 72.63mm dimension is the 2.968" “B” value of the 5HA, but then dimension “D” is not the same. Dimension “D” of the diff I’m working on is the same as the 4HA. Using the 5HA dimension “B” would result in a circa 3mm shim stack which would not allow the Crown Wheel assembly to assemble with the diff housing and Pinion. This diff is out of an XJS and shows none of the hallmarks of ever being apart after initial assembly.

As I’ve stated in earlier Posts, the 66.67mm “B” dimension will not work, for it would result is a shim stack height of over 6mm for under the Pinion inner bearing cup. If such a shim stack were to be used, it would be impossible to assemble the Crown Wheel assembly with the diff housing and Pinion.

From the picture in my first Post of the 3.31 and 2.88 Pinion Shafts, it can be clearly seen that the thickness of the 2.88 Pinion Gear is thinner than that of the 3.31 shaft. The overall length of the two shafts is the same, meaning that the difference in thickness of the Pinion Gears is via more material being removed (circa 6mm) during manufacture, from the face of the Pinion Gear where the inner bearing seats. It would make Zero sense to remove this material, only to add it back via a circa 6mm stack of shims.

Regards,

Bill

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SalisburyAxleService.pdf (2.2 MB)

I rearranged the pages so they fall in order and did a slight crop to get rid of the black at the bottom. Hopefully it worked!
Mike

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It appears that XJS’ used three different diffs, for the 2.88, Dana, Salibury, and a GKN.

https://jag-lovers.org/books/old-xj-s/finaldrive.htm

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Hello Terry,
The issue with this diff has become more confusing. My measurement of 72.63mm is accurate and there is no scope whatsoever to be able to add a circa 6mm spacer so that the dimension “B” of 66 67mm can be used in calculations.

I recalled that I had purchased a 2.88 gear set a few years ago and therefore, I dug that out to confirm that 2.88:1 ratio differentials must use a different dimension “B”, something close to 72.63mm, perhaps 2 7/8". When I compared the two 2.88 pinion shafts (see the picture below), to my surprise, the one from the gearset I’d purchased, had the same axial position of the inner bearing as the 3.31 pinion shaft. Accordingly, this particular pinion shaft would relate to the 66.67mm dimension “B”. However, the Crown wheel assembly won’t assemble with the pinion shaft of the differential I’m working on if the pinion shaft is made conform to the 66.67mm dimension “B”.

IMG_0993
IMG_09931920×2560 370 KB

I have the original shims from the side bearings of the diff centre (those used to set the backlash between the gears), and I had bagged them as L and R sets. As it turned out, the two shim stacks were the same, and as I had only got to the point of getting the correct shim stack to obtain the correct pre-load for the side bearing, the shim stack height per side of the assembly were the same.

I fitted the Crown-wheel assembly and with no shims under the Pinion Bearing Cup, had a backlash reading of around 0.025" (circa 0.6mm). Using an educated guess, I assembled the Pinion Shaft Inner Bearing Cup with a 0.7mm shim and this reduced the backlash to 0.25mm (0.010").

The witness marks on the drive side of the Crown-wheel gear teeth look reasonable, with perhaps a tendency of having too little backlash. There is no specified backlash amount engraved on the Crown-wheel anywhere, so I’m reluctant to reduce the backlash further, for the gear teeth witness marks are indicating a slight bias towards being too little backlash, but then on the other hand, 0.25mm (0.01") backlash is getting up there.

The Differential housing is definitely a Salsbury, but the configuration of the Crown-wheel seems to take up the difference in the axial position of the Pinion Gear.

Regards,

Bill

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Hi Bill. I wondered if you wound up, somehow, with one of the GDK differentials used on the XJS and that might explain the issues, but I’m really not experienced enough to be of much assistance to you. I wanted to get active and help you locate specs for your job - something I can do - to thank you for all the invaluable assistance you’ve provided to me and other prospective “gearheads” over the last few years, on bearings, hubs, and differentials. Thank you. Look forward to more!

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Thanks for that Terry,’

Regards,

Bill