XJS Crown wheel and pinion in my e type housing

[Steve1967]

Hello, I managed to get hold of a Powerlok XJS diff with a 3.07:1 ratio and intend to replace my E types 3.54:1 crown wheel and pinion with the one from the XJS.

I know the external measurement of the XJS unit is about 1" wider than the E Type's but I am told the internal measurements are the same and the Crown Wheel and Pinion interchangeable. Can anyone confirm if this is the case or not? Are there any pitfalls?

Obviously I shall replace all the bearings and oil seals as a matter of course.

Many thanks for your help and any advice there might be out there.

Steve - Tewkesbury

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[Steve1967]

Sorry I meant to say that my car is a S1 4.2 roadster. Not a V12 as my avatar might suggest!

Steve

[mgcjag]

Hi Steve..there are good guys ar Universal Axles Kidderminster that could help.....no connection other than having a couple of axels and one converted to 3.07 done there.... Steve

[Steve1967]

Thanks Steve, thats interesting, I may well give them a call. Thank you.

Steve

[44DHR]

Steve,
Bit unsure what you mean by that you have been told that the “internal measurements are the same”, but all Differential units in Jaguar independent suspensions with Salisbury 4HA Differentials are the same, with 3 variations on the designs of the output shafts and their bearing housings over the years and the earlier units having separate brake brackets before they were cast into the casings in later units.
With regard the XJS Differential this is a straight swop - I have done several - but the lower Inner Fulcrum Brackets must be retained from the E Type differential and fitted and shimmed to the XJS differential as these allow the unit to align into the E Type rear suspension cage. We have covered this subject several times before in this forum, especially the differences in the Fulcrum Brackets.
viewtopic.php?f=3&t=10004&hilit=Inner+fulcrum+brackets
Depending on the condition of your Series 1 differential, I personally don’t usually remove the XJS Crownwheel and Pinion and have the various issues to set up the tolerances in a different case, but fit the whole XJS differential - once fully inspecting the unit.
Trust this assists,
Regards,
Dave

[Series1 Stu]

Hi Dave

When you say replace the whole differential, do you mean the complete final drive unit, the differential being housed within the unit?

I know it may seem a little pedantic but, to avoid confusion, clarity is essential in these types of discussions.

Regards

[44DHR]

Yes Stuart, the complete final drive unit, if it is a Salisbury 4HA differential. As in photos of a unit on the bench in my post on the second page of my referenced previous post above. That is a XJS differential unit before it was fitted into an E type cage, showing the reason why the correct E Type fulcrum brackets must be fitted.
The complete differential in its casing, right from the drive Pinion through to the two output shafts, with just the two lower inner fulcrum shafts fitted from the E type differential. I use the “normal” pressed steel diff cover rather than an alloy finned cover if the XJS differential came with one.
Regards,
Dave

[Steve1967]

Hi Dave, thank you for your detailed reply and the link - which was really informative.

Unfortunately my car is not a matching numbers car but even so as I am into a total rebuild and plan to renew all the bearings and oil seals anyway. I may as well retain the S1 diff casing as this looks quite different to the more chunky XJS diff. Also the features such as the brake brackets etc are all important to the car I think.

I will keep the original diff now I know the Crown wheel and pinion will all fit.

Thanks for your help and assistance.

My best regards

Steve