The first XJ-S appeared in 1975 as a 1976 model. Power came from the Jaguar V-12 petrol engine with a choice of a manual or automatic transmission, but the manual was soon dropped. V-12 automobiles were unusual at the time, with notable others coming from Italian luxury sports car makers Lamborghini and Ferrari. The specifications of the XJ-S compared well with both Italian cars; it was able to accelerate to 60mph (97km/ h) in 8.9 seconds and reach 142mph (229km/ h). The first series of XJ-S cars had a Borg-Warner Model 12 transmission with a cast iron case and a bolt-on bell-housing. In 1979 GM Turbo-Hydromatic 400 transmissions were fitted. The TH400 transmission was an all aluminium alloy case with an integrated non-detachable bell-housing.
Jaguar's timing was not good; the car was launched in the wake of a fuel crisis, and the market for a 5.3-litre V12 grand tourer was very small. The styling was also the subject of criticism, including the "flying buttresses" behind the windows.