Will a transmission from a 2000 XJ8 fit in a 1997 XK8? Thanks

 

It's a little hard to say, if you had the VINs for both vehicles I could tell more from the parts catalogue. They are both ZF5HP24s, but might have small differences, for example you might have to swap over the "extension housing" as Jag calls it, the piece out the back where the driveshaft goes in.

 

. . . and the Transmission Control Module might have something to say about it also as well as the Engine Control Module.