Seies 3 V12 Differential XJS

clive V12 · Post by **clive V12** » Sat Oct 24, 2009 8:53 pm

Hi,
I have now replaced my broken shocks, at the same time I replaced the springs, discs, pads and renewed the caliper pisons and rubbers, buy I still have a speed related kocking from the back end, I think it may be the diff!
Does anyone know if the Diff from a 1978 XJS V12 will fit straight into a seies 3 V12 E Type ?
If not can you recomend someone who can rebuild my diff ?
What is the aprox cost ?
Regards,
Clive

christopher storey · Post by **christopher storey** » Sun Oct 25, 2009 8:21 am

There's a chap called Eric ( not a lot of use I know!) in Northampton who rebuilds diffs. A search of E type club magazines will probably give his contact details. IIRC cost was about ? 900 .

if I may suggest it, get your car up on a ramp, with both rear wheels off the tracks, and then run the car in gear at a simulated 30 mph and try to find your knock with a rubber tube in your ear

clive V12 · Post by **clive V12** » Sun Oct 25, 2009 8:40 am

Hi Chris,
Can please elaborate on the rubber tube method of locating the knocking.
Regards,
Clive.

christopher storey · Post by **christopher storey** » Sun Oct 25, 2009 6:44 pm

Clive : with the wheels rotating on a ramp you may be able to locate the knock without any artificial aid. However, to localise a sound precisely sometimes is more difficult and of course you do not want to put your ear close to rotating machinery. A smallish bore ( 1/4 inch/ 6mm) rubber or plastic tube stuck in one ear is amazingly sensitive in that you can move it around without putting fingers at risk and when the knock grows louder you know are moving in the right direction. Exceptionally good for locating those "whispering" exhaust leaks from a pinhole in a joint etc. You can use it in your case as a stethoscope for the final drive unit. If you press the open end against the casing ( or the backplate which is thinner) , you should be able to hear any untoward noises from inside very clearly

Just as an afterthought, you have eliminated driveshaft universal joint wear have you? This is a common cause of a clicking noise from the rear

clive V12 · Post by **clive V12** » Sun Oct 25, 2009 7:37 pm

Hi Chris,
Thanks for the help, I will try this method.
Yes I have eliminated the drive shafts UJ`s by disconnecting them.
I will let you know my results.
I would still like to know if a XJS diff will fit into a Series 3 V12 ?
Regards,
Clive

MarkE · Post by **MarkE** » Sun Oct 25, 2009 9:45 pm

I'm pretty sure it will fit, Clive, but most XJSs' had the 2.88 ratio fitted. Fine for high speed crusing, but surely not what an E Type is about. I don't think it would do your clutch much good on a hill start either!

Post by **Heuer** » Sun Oct 25, 2009 10:50 pm

I have a 2.88 diff, albeit with a VSE02 spec engine, and it works well with a 5 speed box.

"Fine for high speed cruising, but surely not what an E Type is about" - I thought that is what it was all about; crossing continents with grace, pace and space! (OK not the last one in an OTS).

MarkE · Post by **MarkE** » Mon Oct 26, 2009 9:43 am

The standard is 3.31 for the S3 manual, a bit lower (numerically) for the auto, and that feels pretty right for the 4 speed.

I'm sure that London to Athens would be a great cruse in an E Type, but most of us in the UK, most of the time, just thrash about the A roads and motorways, so really, I don't see the point of an 'overdrive;' diff ratio. Once you're above 90 mph, in the S3 at least, the wind noise is so loud that it drowns out the engine noise...which in the V12 isn't very intrusive in any case.

It's becoming increasingly popular to change the diff in the XJS to a higher ratio one from an XJ6, giving a lot more fun at the sort of speeds we really drive at.

But each to their own!

clive V12 · Post by **clive V12** » Mon Oct 26, 2009 11:26 am

Hi Mark,
So can I assume from your information the diff from a XJS and XJ6 will both fit straight into a E TYPE series 3 ?
Regards,
Clive.

MarkE · Post by **MarkE** » Mon Oct 26, 2009 3:02 pm

I assume so, Clive. I've had a S3 diff put into an XJS, and there were no problems. The later (facelift) XJS may be different as they had outboard discs.

A couple of things to bear in mind. The XJS is a much heavier car, and the diffs do wear in them. I've had a couple replaced at 90k miles or so. A rusty XJS is worth all of ?50 for the whole car, so don't spend too much, especially if it's an unknown quantity.

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