Hello all, I'm considering adding a XK8 or XKR to the garage and have a few simple questions. (I'm very familiar w/S-types and prefer the 4.2L w/ZF 6 speed drivetrain. Currently have an 03 4.2L that in prime condition)

1. What years had the 4.2L w/ZF 6 speed?
2. Can the XK8/R be tuned? I don't want to do much for power. I mostly want to change transmission shift points and shift firmness. Also to correct for rear gear changes.
3. How complex is it to change the rear diff to a steeper gear and add some kind of posi traction?

Ideally I'd like a coupe w/less than 60k miles, 4.2L engine, and I'd be open to it needing some (normal) mechanical attention.
Of coarse a clean KXR would be nice but I need to keep the entire cost of getting the car, modifying it, and bringing it up to my standards, to <$20k
(I like to do all my own work so generally I don't pay for labor. Only parts and tuning software)

 

1) 2003+
2) In a word, no. There have been rumors but nothing that has been substantiated or commercially available.
3) Rear gear, no way. For a LSD you are limited to a Quaife unless you change the pumpkin.

 

Thanks for the reply.

So say I were to either change diff gears or put in a custom pumpkin... how can I make the cars computer/s accept the different ratio? Can a dealership do that?

Anyone try this -> https://www.paramount-performance.co...ku1755411.html

 

Dealer cannot change the rear ratio and programming the ZF is notoriously difficult. If you had an earlier 4.0 XKR with the Mercedes box then it can be done, even if it is expensive.

Not many have tried the tuning options that do exist for an xk8/R. The general consensus here on the forum is that they are snake oil and there a not any published before and after dyno results that I have ever seen.

Most that have gone for big power have either not tuned the ECU at all or done a full custom setup.