I would like to take out the 4.0 Liter engine and 5-speed transmission (gearbox) for a 5.0 Liter engine and 6-speed transmission (gearbox). I have been told that it is financially/electronically less than feasible.

I'd appreciate some input.

Thanks in advance.

 

Speaking out of school, I think it would require a lot of re-coding of the DME, or whatever Jag calls it. The engine management portion would be completely different. The 6 speed has the controller integrated into the valve body, so there is no longer an external trans control module. Maybe one could swap out the DME with one from a 5 liter car, but that opens another can of worms with security.

I forget the name, but there's a company that specializes in LS swaps and they have worked out all the electronics. Maybe that's a better way?

This brings up a question I've had for a while. If I understand it, the only internal difference between the 4.0 and 4.2 is the stroke length. If that's true, could one swap a 4.2 crank into a 4.0? Would the engine management be able to compensate for the added displacement? Could the injectors keep up?

 

You would need to buy a 5.0 XK first because you would need all the modules and wiring for a start. You would need to take all that out of the 5.0 car and implant it into the 4.0 car and find space and room for all the wiring, modules, engine and transmission. It's not something worth doing if you had a working 5.0 XK and a working 4.0 XK. Might as well just keep both or pick one or the other. As for cost and time well it would take a hell of a lot of money and time. Going down a manula conversion for the 4.0 or an LS V8 conversion would probbaly be an easier option just because other people have already done that but as far as I know no one has taken out the 5.0 V8 from the last XK's and put them into the early 4.0 XK's.

 

The only path that makes any financial sense is to sell your 4.0 car then purchase the 5.0 car.


if money is no object and you can’t do without the 4.0 car’s styling, then yes, it can be done. As mentioned previously, buy the 5.0 car and transfer the drivetrain and the entire electronic system, modules and dash displays, etc. into the 4.0 shell.

aside from the money pit this endeavor will create, it’s going to be very time consuming for you or the shop that takes on this project. Two to four years is my estimate.

Can you wait that long to drive the Frankenstein car ?

Z

 

It would take a lot of time and money, but I do want to see it done and support your decision of doing something financially nonsensical but that would make for an outright riot of a car. Although, if you're going that far, why go with the 6-speed ZF box and not the 8-speed (if it fits), or a manual box with custom standalone ECU?

 

Thanks to all. (This was just a thought).