Hello guys

Sorry for banging on about this old chestnut again.

Considering an LSD again for my 99 XK. It got a bit slippy when I tried to pull away on a wet road at the roundabout the other day The Quaiffe is the industry standard but I have heard varying reports that it does not work well with the XKR ESP.

Also it is very expensive.

With that in mind I was considering a reconditioned one from an old XJS or similar.

Does anyone know if an LSD from an older Jag would work and fit on a 99 XKR?

I might be wrong but I thought that maybe the bespoke older Jaguar unit would be better for a more modern Jag than a after market alternative

Thanks.

 

Xjs won't work. Housing is wrong and gear set is different. The 15HU units in the X100 has a centre line pinion while pretty much all previous jags had offset pinions.
The 14HU units will bolt in with some small complications. Biggest complication will be any ratio change but nothing insurmountable.
Do a thread search for "diff type and ratio change"
I did have an old thread around 12 months ago on my change over.

 

The TCM will NOT accept a different ratio. The HU 14 is a CENTERLINE diff and the HU 15 is fitted to XJ40 and X300 sedans.
The HU 15 Limited Slip is identified as an ORANGE colored tag with a BLACK X.
I installed a Quaiffe unit along with a 3.27:1 HU 14 (imported from a Mexican XK8) into a customer 4.0 XKR but the TCM was sent out for a 'reprogram' to accept the ratio.

If you do get the HU15 with Limited Slip to fit properly you MUST select a ratio the same as the one you are replacing OR reconfigure the TCM.

The rear suspension front plate will need to be replaced as the pinion shaft is offset and then the propshaft 'might' interfere with the body 'tunnel'.

The HU 15 is supposed to handle more torque than the HU 14?

The only cars that use the 3.27:1 HU 14 centerline diff are the 3.2 X308 sedan ROW and XK8 Mexico. The US never had any engine except the 4.0 for the X100 and X308.

 

Discussed years ago.

https://www.jaguarforums.com/forum/x...f-swap-141802/

 

l have CAN work around for ratio change compliments of Chirpy. Running 3.27 HU15 LSD and faultless performance.
To correct my earlier post, l transposed the 14 and 15HU's, sorry.
I posted a thread about 12 months ago detailing the swap but don't know how to link it.
https://www.jaguarforums.com/forum/x...change-251133/

 

Thanks mate, I thought probably an old unit would not fit otherwise I guess everyone would have been at it. It is a shame that the S1 XKR was not given an LSD ... I can understand why the original XK8 had a standard open diff as it was launched as a GT... but the R when it came out had the CATS adaptive suspension and with the extra supercharger 80BHP it needed an LSD... IMVHO 🤣

Will live with it, I don't do any vigorous driving these days. Thanks 👍

 

Electronics are cheaper than mechanical most times. (Traction Control vs Limited Slip)

 

My knowledge is pretty limited..can I ask what is the best type of LSD for my 1999 XKR, geared or plated ? I have heard that the Quaiffe is a brilliant system but is more aimed for racing and does not work all that well with the traction control on for every day use.
Any advice greatly appreciated 👍
Thanks, Smitty

 

Very true, but I am old school. Traction control is a crude electronic device which just cuts the power as a safety measure. An LSD allows a smooth transfer of torque biasing for a better driving experience.

IMVHO 🥰👍

 

Unless you have a modern Ferrari which I can only dream of. The traction control system is more complex and advanced than the Space Shuttle 🤣
Personally I am not sure I would want that in a car. Think the car would be driving me, not the other way round. Perhaps designed for fat useless driver rich businessmen to show off to "mates at golf club" 🤣
Again just my humble opinion

 

From what I have read, geared vs plated/clutch operation of the lsd is a bit of personal preference, e.g. intentionally locking/sliding rear out of tight corners with clutch based. Also, depending on the target diff you choose, your choice can be limited - my understanding is:
- Going with the factory stock HU14, I think Quaife gear based is about the only option. Advantage is fairly easy install, downside is expense. Additional downside is that HU14 crown/pinion is weak, several anecdotes of chipped/lost gear teeth if pushed hard, which is likely the reason to get an lsd in the first place, additionally side bearings possibly can wear quickly.
- Swapping to the stronger HU15 (larger diameter) clutch based lsd from XJ6/XJ12 means changing out front/nose bracket on rear suspension/etc., since pinion is offset vs centered on HU14 (per baxtor/motocarman), but cheaper since you can get a used one and grab bracket etc. at the same time.
The easier mechanical option for HU15 is to live with a ratio change and re-program TCM at vast expense if you can find a commercial service, or do the CANBUS workaround if you are handy with electronics. Main options are 3.27 from an X300 XJR or 3.58 from earlier XJ6/12 (noting many XJ6/XJ40 are open diff, need to find lsd option with the black cross tag), vs. stock 3.06 HU14 ratio (per motorcarman there were some 3.27 HU14 options, but not with Mercedes TCM/XKR, only ZF ). Likely worth replacing the clutch plates but nothing else. Baxtor covered all the details.
Or you can source Dana44 crown and pinion to get 3.06 ratio (if such is available...) and stay with stock TCM, but then you have to setup the new internals, lots of shimming and preload checks, etc. Also you could change the internals to Auburn (clutch) or Eaton/Detroit (gear) - 19 spline Dana44 - if you prefer, as well as have full flexibility on ratio, e.g. 3.73/3.77 is an option.