This isn't the usual question, more of an observation of something that might be interesting to 240 owners, anyone looking for a secondhand gearbox (and Jaguar anoraks). The 3.4 and 3.8 Mk2s had all sync boxes with the prefix JC for without overdrive and JCN for those with o/d. I don't think any other cars received boxes with these numbers. They were unusual in having very long tails, longer than those of the S type. 420, or XJ. Authors don't seem to agree on the box fitted to the 240. From what I can discover, some 240 cars were fitted with JC/JCN boxes and others with a gearbox pre-fixed KC or KCN. While the JC/JCN had what were at the time usually referred to as the 'standard ratios,' KC/KCN had the gear ratios of the E-type's close ratio gearbox. In fact, the commonality of parts with the E-type is confirmed in the parts lists of the usual suppliers.

In the road tests of the time, the 240 tested by 'Autocar' was, from the ratios listed and max speed in gears, a KCN box, while the one tested by 'Motor' was, for the same reasons, a non-o/d JC box. The road tests can be found in 'Brooklands' reprints. A few years ago in this forum, MussieRon was seeking info on his 240 and it turned out his gearbox (from the chassis plate) was a JCN (* link below). The 240 box that I bought a while back is a KCN. It's hard to say for sure, but it gives the impression that Jaguar were simply using up stock. On the other hand, the KCN is unique to the 240. Had Jaguar considered and abandoned a close ratio with overdrive E-type or was it merely an excess of close ratio gear sets?

Any thoughts or disagreement are most welcome.

* MK2 1968 Identification - Jaguar Forums - Jaguar Enthusiasts Forum https://share.google/fnrKK7vxY4kNKIr93

 

Hi, my 240 is from Jan 1968, RH drive with manual gearbox and overdrive.
gearbox is confined original and is a JCN.

 

Thanks for the info Chris. It looks as though the choice of gearbox was completely random.