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XJ6 & XJ12 Series I, II & III 1968-1992

Rebuilding /re-gearing the Differential

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Old 05-07-2013, 03:54 PM
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Default Rebuilding /re-gearing the Differential

I'm rebuilding the differential from a '73 XJ12 (S1) to be used in a 1959 Tojeiro sports racer (). I was hoping to use the ring and pinion from a '84 XJ6 to give the car some legs out to 155 mph on the track. However it appears that the XJ6 2.88:1 ring/pinion binds when the carrier is installed. I did notice that the LSD and standard carrier had slightly different offsets for the ring gear mounting flange.

I've read that the XJ12 or XJ-S had a 2.88:1 gear set installed on the Salisbury LSD. I'm guessing that the LSD 2.88:1 gear set is different from the standard 2.88:1 gear set. If this is the case, I'd be willing to trade my 3.31:1 gear set for your 2.88:1 gear set if it will work my my '73 XJ12 Salisbury LSD diff/carrier.

Also, what a pain to set the pinion depth! I'm supposed to use Jag "setting block 4HA" to zero the depth gauge, but I can't find that block anywheref. Why in the world didn't they just give us the actual measurement of the "setting block"? Does anyone here know what that measurement is?


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Old 05-07-2013, 09:34 PM
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Default treat it like a 19 spline dana44

It's just a 19 spline Dana 44. Get a Eaton or Auburn LSD and use any gear set you want. You can even re use the jag gears. Eaton and Auburn offer tall and short offset LSD units...simply get the tall one ad reuse your 2.88 gears or just get a new gear set. Then get a set of standard side bearing and a jag pinion bearing and your are done, assemble like a dana 44 and you are done. Don't pay attention to the subterfuge you read on the internet. Its no more complex then any other dana 44. I've done it so I know.

Trading a 2.88 for a 3.31 is a good idea. Post that up on the XJS board and you'll get some bites. However It would be cheaper and easier to use a new eaton or auburn LSD then to rebuild the jag unit with new jag bearings. The jag uses odd sized bearings and they are expensive. The auburn or eaton uses a common bearing so its far cheaper. The Jag unit uses dana 44 clutches which are cheap enough but the jag steels are pricey. I've done the a costs bit less to use a new Eaton locker then to rebuild the jag LSD unit.
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Old 05-08-2013, 12:01 AM
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Originally Posted by Untame View Post
I'm rebuilding the differential from a '73 XJ12 (S1) to be used in a 1959 Tojeiro sports racer ().
I know its off topic but you need to post some pics! To say thats a rare bird is an understatement.
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Old 05-08-2013, 07:29 AM
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Pictures are at Coachsmithing -- Delahaye, Bugatti, Ferrari

I've already rebuilt the carrier, and I've purchased all of the bearings. I am doing the shim fitment before I blast and refinish the housing.

From what I've read elsewhere online the 2.88 gear set I have is a "thick" set from a standard carrier. I'm thinking about having the back side of the crown/ring gear cut down and re-hardened. UNLESS... there is an LSD 2.88 gear set that would work on my 3.31 carrier.

Then again, trading someone else might be the best option. If I go with the 3.31 gears my top speed drops to 135 mph from 155 mph, and that would be disappointing.
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Old 05-08-2013, 07:31 AM
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Anyone have a clue on the standard pinion depth measurement or the actual measurement of SL.3 "setting block" F.H.A.?
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Old 05-08-2013, 09:43 AM
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Default Check with Curt Hamiliton

He has been building/modifying Jag IRS for many years. Has all the parts, tools
and knowledge to do anything to these units.

He fixed my bent swing arms in minutes!

Curt Hamilton
W (818)787-9695
Cell - (818)943-2323

15826 Stagg Street
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288, 73, depth, differential, fha, gears, jaguar, pinion, power, rebuild, ring, set, tear, xj6, xk8

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