[xk] Gearbox Ratios

Sorry Russell - cant help,
I am struggling to be all that interested in such ‘modern’ cars, and indeed am aware that the later cars Service and Spare Parts publications are very limited/if at all with such information, and such late ‘manual’ gearboxes are never/rarely seen in Australia to check such things physically…
Indeed, I was always under the impression that V12 XJS were never supplied with a Manual Gearbox - maybe a prototype - but never for sale to the public. Certainly the XJS fitted with 6-cylinder engine was available with a manual gearbox, with a local friend having one imported second-hand from UK, again not sold new in Australia, and no I was never interested enough to check the Gearbox Number - but having said that was probably the nicest XJS I have ever driven,
Same situation with 3.4 Series 2 XJ6 - not sold new in Australia, and doubtful any would be imported second hand - entry level XJ6 not a popular model to import, albeit then again I did have another friend import a 2.9 litre Manual Gearbox XJ40…
So maybe someone in UK where these 3.4 S2 XJ6 cars were sold new may be able to advise, albeit I really think unlikely to be different from same age 4.2 S2 XJ6…

There may be something in the 1970s SERVICE BULLETINS that if I get a chance to dig these out from storage I will check…
An April 1973 SB mentions KFN prefix for XJ6 Gearbox and KL prefix for E V12 but couldn’t quickly see anything in later 1970s Bulletins re Manual Gearboxes - all about Automatics…, but again these are not UK Bulletins that are more likely to mention matters Manual Gearbox in Series 2 XJ6…

I am fairly sure all the 6 cyl XJS’s had getrag manual box
I do believe very early V12 XJS’s had 4 speed jag box Roadbend;s did pull one out years ago and fitted jap 5 speed I have the box in pieces here somewhere

It is interesting to hear that you have one of those boxes in bits - would it be possible to share the prefix letters of the number?

Thanks Roger
It seems that there were a few hundred 4 speed v12 xjs’s. The service manual does not reveal the gearbox prefix (as might be found with the 1960’s cars)

It is interesting to hear that there were no 3.4 xj6 sold here - i certainly have never seen one. Annoyingly I dont have a genuine repair manual for the xj6 in my library, but my Autobooks one mentions only the KFN 2.933 box- no mention of the 3.4 at all and no discussion of a later ratio change

Yes, I checked Skilleters XJS Collectors Guide…

"There are no special problems to be wary of. The Jaguar manual four-speed box occasionally fitted to early cars between 1976 and 1979 is an unburstable unit, although after high mileage the syncromesh can weaken …

"The six-cylinder gearboxes … Getrag five-speed…

So sounds like the V12 XJS Gearbox would be same as V12 E-type - a KL (with no overdrive, so not KLN), albeit whether the few XJS applications warranted another prefix or not, that is the outstanding question…

Nothing found in the 1970s Service and Spare Parts Bulletins I have quickly checked, but as before would have to best be the Leyland UK Bulletins for anything re manual gearboxes as they seem to have been ‘home market’ only, rather than export…

Well - with different ratios, one might expect a different prefix

1st in the V12 E was 2.933, 1st in the XJ-S was 3.238

it is surprisingly hard to nail this info down

Although- update- I now have a clue that XJ-S boxes might be KM and XJ6 KPN, most likely change over May 1975