What's up with rear end on the XJR...It does not seem to be a limited slip differential...Or at least it doesn't feel it. It just seem to sit there and bake the tires (tire)...No sense in modding if it can't handle the HP it already has...WTF

 

There is no LSD. Instead the car's traction control system uses the rear brakes to stop wheel spin when traction is lost. Yeah, I know, it wears out the rear brakes !

 

Thanks...How lame is that...Now I can do some 1 wheel wonders! Guess I have some research to do...

 

I believe Quaife make a torque biasing differential (similar to a 'Torsen') that will fit an X350.

Edit: yeh try Googling - 'jaguar x350 quaife'

 

This is what the workshop manual says about traction control:

" Traction control is an additional function added to the ABS/DSC system. The vehicles driven wheels are continually monitored for wheel spin relative to the calculated reference speed and to each other. If wheel spin is detected, the traction control function intervenes independently of the driver, applying brake pressure to the slipping wheel and reducing the engine drive torque supply. Meanwhile, brake pressure is modulated by the traction control until traction is re-established. Traction control brake actuation is diminished above 40 km/h (25 mph). Above this speed traction control relies primarily on engine torque reduction. "

My experience is that the torque reduction when a wheel is slipping is virtually complete ie almost to zero. T/C is most definitely not a substitute for a LSD

 

Thanks for the info...Like I really want my brakes automaticly applied when I am accelerating...Gotta do wonders for your 1/4 ET!!!

 

My impression is that the system is far more 'interested' in stopping the spinning wheel than it is on maintaining much torque on the other one.

 

Unfortunately, the electronics are now cheaper than a mechanical LSD, hence the use of the brakes to stop wheelspin. This is because the mechanism is already present for the anti-lock brake system.


The first time I had a service after buying the car, I was told the rear discs and pads needed replacement. "How come" I said, (as we all know the front brakes do most of the braking). "Ah, but the car uses the rear brakes as well as you, to stop wheelspin when you're wellying it" said the dealer service man. So a set of discs and pads where fitted, and I got my introduction to the modern car !!

 

This is one of the reasons I'm thinking about getting rid of my XJR, even with high performance Yoko V105s, I can't take off fast without the traction control kicking in. The other reason is the suspension sucks. I can appreciate a soft ride but not to the expense of feeling unsafe. The car does not feel planted at all. It feels like I'm driving on a suspension made out of Jello. It also sways side to side. I'm not sure if this is how it is supposed to feel or something wore out. My 2013 Grand Cherokee feels safer and I have more confidence when cornering hard. On the Jaguar it feels like it is going to flip if I corner at the same speed I do in the Jeep. It's a freaking SUV!

Anyways,

Cheers it's Friday.

 

I actually am running a set of dunlops off my friends Nissan GTR currently. Can handles pretty dam good honestly. Tires are a bit taller than stock and if you have an air ride issue and try to turn..Bye by fender lip....Ask me how i know...ANYWAYS


Bottom line is you need to get a quaife. Its the only fix. I currently only have exhaust and air intake and the car is a handful. Its sad that such a refined ride has such an awfully intrusive traction control system. It feels awful. Anything but smooth. even with the meaty sticky 285's outback it will spin, hop, trac control and torque limit all the fun away/. Even when you shut the trac control off its still there as you can feel the torque limiting feature kick in. And I don't think it was a cost issue. I've had cars in the past that had limited slip in the manual version and this crap in the automatic version....Automatic versions always costing more of course. Never really felt right


Anyways I still have a nice shiny 2.1 autorotor sitting on my shelf to be installed...And I refuse to do it until I fix this little issue. I picked up an early xjr diff and housing for my xkr (that means reasonably priced). That fixed that issue. But this car........

 

I have the Quaife in my XJR. It's a massive improvement over the stock open diff.

It used to be that Quaife was the only option, but there is another way, using the diff and driveshafts from a 4.0L S-Type. That diff will accept a standard Ford 8.8" 28-spline LSD center.

You need to swap your gears over as the 4.0L S-Type had 3.31 gears, the XJR & STR has 2.87's. So a full rebuild would be on the cards. But i've looked at it a couple of times and in the end it would still be a cheaper exercise than just the buy price for the Quaife ATB...

Or you could keep the 3.31's, but that needs re-programming, which is also an option now...

 

I've thought about fitting a Quaife to mine: it's only a Tdvi but the peak torque (second only to the XJR) is low down and it can catch you out when turning out of a junction and giving just a moderate amount of 'welly' if the the road surface is a wee bit loose.

 

How difficult is it for a DIYer to fit a Quaife Cambo?

With the mods I have done the "slip" on the rear even under moderate acceleration is pretty bad.

 

Like to do LSD but for 2K I will pass...

 

If I knew that I could install a Quaife unit myself I would purchase it.

This is something I have to research.

 

Several people have done it themselves, have a look here on the forum also in the X150 XK/XKR subforum (same diff). https://www.jaguarforums.com/forum/x...lation-155867/ although there are several chassis items in the XK that aren't in the XJ (like the chassis reinforcing bracket).

The price of the Quaife is outrageous now though, when I bought mine 4 years ago it was cheaper, also the currency was better for me (buying out of the UK in GBP, but I was getting paid in Swiss Francs)

I think the 4.0L S-Type conversion will be a cheaper way to go these days, easily under $700 in parts if you shop smart.

 

I will do some research on the 4.0L S-Type conversion.

 

This would seem to be the better alternative as
the Ford or aftermarket LSD are available in multiple
types from mild to wild.

With the Quaife, you have one choice for approximately
three times the money.