What are the ratios in our 6 speeds. Especially the overdrive. Was thinking why have a overdrive trans and not use it to get some more giddy up with gears like 3:42s instead of our 3:06s.
I know it will loose MPG but it's not a daily driver.

Here is the specification for the transmission and rear axle.

Problem with changing the gears is that you have to reprogram the transmission controller so that it won't go into limp mode, but no one seems to know how to do that for the ZF.

That's it. And no one knows how to do it? Someone knows.
As an ex drag racer I know the benefits of gearing especially with a 6 speed overdrive. It's hands down the best mod to make the car quicker. The XK8 runs mid 14s Im sure it could be a 13 sec. car easy with gearing and still cruise the highway with ease.

If you find someone who can do it, at a reasonable price, you will have forum members lined up to make that mod.

I have searched the world, there is no one who can reprogram the ZF trans in our cars...

https://www.jaguarforums.com/forum/g...ids-sdd-77299/

Well that sucks!