Mark V Transmission

I “saved” a Mark IV by finding a Mark V engine and transmission. The transmission has a few missing teeth, etc. Will an XK 120 transmission bolt to this engine? Another solution might be to find new gears or another Mark V transmission. Any ideas would be appreciated.

what is the serial number of the transmission ?

The number on the transmission is J H 2164

I see J H 2164 stamped on top.

Ok then that transmission series was also used on the early 120s

JH2164 Gearbox is 99.9% probably ex a January 1950 Mark V Jaguar, and most unlikely to be from anything else.

See attached picture of a local friends January 1950 Mark V ID plate, typically for Australian new Mark Vs with the lower lubrication recommendations of the ID Plate cut-off, with the local Distributor BRYLAWS attaching their own local lubrication recommendations instead.

But note this Mark Vs Gearbox Number - JH2159 - five numbers earlier.

Now you need to be careful, as although the internal gears/shafts etc of a Mark V JHxxx series Gearbox are interchangeable/the same as an XK120 JHxxx series gearbox, you need to check all the external detail to ascertain whether the gearbox installation will go straight onto an XK engine, and into an XK120 chassis re mounting points, gear-selection, speedo drive location, and output flange and its location. A close comparison of the Mark V Spare Parts Catalogue JH series gearbox against the XK120 Spare Parts Catalogue JH series gearbox will tell all.


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I think it will interchange without problems. The XK 120 uses the same gearbox mount as a MK IV
Although technically on a MK IV the 2 steel plates should be ata slight angle to each other not parallel. I’m not sure about XK120 as no one seems to bother with this, Just put the rubber bonding under a bit of pre stress.
Mixing parts from different series might be an issue , but whole boxes go straight in

Thank all of you for the information. I know a restoration mechanic that has worked on XK 120, 140 150 for many years. He has not worked on a Mark V transmission. Your information tells me that he will be able to repair mine. Several 120 owners have switched to 5 speeds and he should have extra parts and 120 transmissions. He is an hours drive away…now I will drag the car over to him.

Hello Dennis, if it seems appropriate would you share the name of the person or business who might handle your transmission work? Being also in Southern California (Irvine) and with a Mark V there may come a time where that contact information could be useful to me.

Hello Roger,

  I just had an XKE restored at Steve's Jaguar in Canoga Park. 

David, who works there as a independent contractor, does all of
the mechanical work himself. He routinely takes all of the gears
out of the transmission as well as the rear end of 120, 140 150
and XKEs. I believe he will have an understanding of these
earlier transmissions.




This is what Ed is referring to, the top and bottom plates of the C.478 gearbox mount are not parallel, because the engine is tilted upwards in front relative to the chassis. But this is true on all models that use this mount, '38 SS through '52 XK120.

BTW early Mark VII with JH or SH boxes had the 4-bolt tailcase pad but did not use it, as they had mounts on the bell housing.

I have JH gearboxes in both my Mark V and XK120 and the only difference is the shift lever. They mate up to both the pushrod and XK types of bell housing. Same speedo drive, driveshaft flange, etc.

Of course there’s always the possibility that somebody swapped gears in one after it left the factory, put in close ratio gears made for a later box; it’s the sort of thing that might have happened to a 120 back in the day.

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Probably not relevant but in the SS and MkIV the 3.5 litre uses a larger flywheel than the 2.5 litre and so it’s worth noting that whilst the gearboxes are swappable the bellhousings are not. Looking at the parts lists for the MkV I see that there are different part numbers for the 2.5 and 3.5 bellhousings so I assume the difference still exists.