www.jec.org.uk

I have a 1981 XJS HE which I'm restoring. I prefer auto boxes but don't like the gearing of the original 3 speed box which doesn't get into the power band until you're doing 90mph+. Does anyone know of a later GM auto box, perhaps a 5 speed, that might fit onto a V12?

Don't wish to dampen your spirits but the 4 speed GM box as fitted to the Facelift 6.0 lt is electronic. It works with it's own computer and the big ecu to select and change gears. Very nicely in sport mode!
Saw one on E bay for £100. Fitting should be simple but getting it to work will be involved if you're not capable of your own service and repair it will cost you a fortune. If you can find an electonics savy mechanic.
Cheaper, in the long run to sell the car and get a 4.0 lt manual.
Best manual solution for the 12 is Keisler....if you can get one in your luggage next time you are in the states.


Don't dream the drive , drive the dream.

Fiatson

Thanks. I am being driven to the conclusion that a good manual box is the answer. I know I should sell the old heap but I'm going to hang on to it. You're right, the expense is considerable.

Dear alex

the later box will only fit behind the later engine because of bolt patern
the main problem that you have is the fact that the box tells you what to do and not you.

the answer is to go clutchless manule so that you control when you change the gear so accessing the power curve

best regards
hyper