My XJ12 has such long legs and with the price of gas I dont see taking it on the open road too often.

I could imagine that the power would be quite thrilling with a higher gear ratio?

I dont know what it is stock but is this a swap that is ever done? what would be the downside besides sub 10mpg?

-Andy

 

It probably has the 3.58 ratio. You can search around for the 3.77 diff.

I went from a 3.27 to a 3.58 in my XJR and I dropped exactly 1 mpg at highway speed. The increase in performance was worth it. Not a night-n-day difference, but a definite improvement

Cheers
DD

 

Is it necessary to replace the entire carrier as a unit or can the gears be swapped?

Is it cheaper/easier to swap the carrier?

any source suggestions?

 

You can probably just swap gears. I'm not positive. I got a rebuilt unit from a liquidator on Ebay. It wasn't really my plan to change ratios but my original diff failed and this 3.58 unit came along at a great price.

Motorcars Ltd, can fix you up, I'm sure

Cheers
DD