I decided to get a Heritage Certificate for my XK8 just for fun really--though I plan to keep this car long-term so I was genuinely interested. I retrieved the engine, transmission, and body numbers from the car using a borescope camera. (Happy to share details on that if anyone wants to know.) When I submitted the info to JDHT, I was told by Tracy Nabbs that the transmission number did not match the build register's. I re-checked it; the sticker on the front of the bell housing with the QR code (mine is a late-model 6HP26) matched the number I found on the raised stamped pad just above the pan toward the rear of the transmission. I've done enough research to know what the model numbers are on these ZF gearboxes and where to find the serial numbers. I had a nearby JLR dealer with a very helpful parts guy go into the Direct Dealer Warranty System to check the number, and the number he got also did not match mine. I don't know if it matches JDHT's because they won't tell you that until they issue the certificate--or so I understand.

So, one of two things is true: the transmission was replaced at some point, or the build register is wrong. (I assume the dealer system gets its info from the build register as well; please correct me if I'm wrong on that.) It would seem that errors in the build register are not unheard-of, at least for older cars--not sure about modern ones like ours.

There is no mention of transmission issues, much less replacement, in the service history on the car, which is otherwise pretty detailed--especially for a Carfax. I contacted ZF North America and they have no record of the unit being remanufactured in North Amercia,and confirmed that it (based on my number) was indeed issues to Jaguar Land Rover for a 4.2L NA V8.

I am going to try to contact the dealership that serviced the car early in its life and the indy shop that did so later, to see if they will tell me if any records they have mention the transmission.

Anyone else have any pertinent experience or knowledge here?