XK150 Gearbox - Not the original but where from

Hi. I am a new member today. Sorry I posted this in the wrong place yesterday (Thanks Gary). I have an XK150 3.4 FHC LHD which was imported from USA to UK many years ago. I purchased it in UK in 2003 and we have only just started the restoration by a restorer in UK who will provide me a restored rolling chassis. Eventually I will be moving the car to Malaysia where I live and I will complete the body and trim. I have found that the gearbox installed is not the original. The Original Gearbox No was 8416-15 according to the Heritage Certificate which I understand was Automatic. The gearbox installed was JLS42191JS with an overdrive. The chassis x member had to be cut away to clear the O/D. I understand that this is a 4 speed manual which has overdrive and would like to know which type of car this may have come from if anyone has any ideas. I have seen other XK150’s advertised with similar gearbox nos.

There are some real funny bits here THAT GEArBOX MOUNTED iN RIGHT SPOT SHOULD HAVE REQUIRED NO moDS TO CHASSIS cross member!
Can you send photos and chassis number of car.
Is this the same graham Jackson originally of Roleystone WA?

Perhaps a MK 1 or 2 rear overdrive case. Instead of cutting away the flange that mounts the rear locating pin, the chassis was cut. Photo of the rear of box as well as chassis will help.

Hi Peter/Terry. Thanks for your comments. Originally I thought some-one had fitted a US Muscle Engine/Gearbox and that was why the cross member had been cut away and pretty badly. My restorer has kept the cutaway but tidied and strengthened it - see last picture after chassis blasting and painting - they say to allow the o/drive to fit - not the gearbox. So gearbox and o/d which has been restored now by specialists will still fit. The chassis number is S835250BW as shown on the nameplate on the firewall. The Heritage certificate for this chassis shows original gearbox was Auto with Gearbox No 8416-15, but it doesn’t say on the certificate that O/D was originally fitted (or not) so I am not sure the sorce of the O/D. Do not have number but can find out. The car was originally despatched to Jaguar Cars New York on 27th Feb 1958 but the first owner was a C C Graeber in California. Hope you can see the pictures

Not MK1 or 2, has the correct top cover and spacer fitted for XK with overdrive, but the overdrive smacks of being 3.8 MK 10, which look similar to the later compact type A item , at least lengthwise. Any chance of a lateral close up of the overdrive?

Unfortunately dont have at moment. But I think the restored gearbox and o/d will have been mated up again by now so will try and get some pictures after I have telecon with restorer tomorrow.



My notes suggest that, with prefix JLS and suffix JS, this is a correct type for the XK150.
This is from the XK150 Spare Parts Catalogue.
The original automatic would have been a 3 speed, no overdrive.
There would have been no reason to cut away the chassis for that one.
It was probably cut away when some unknown third trans was in it at some time.
I would restore the chassis right while you have the opportunity and the body is off.

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Would you have the engine number available and date of manufacture from the Heritage Certificate.
I also agree that you should get the crossmember re established as it was, you do not need the recess for the gearbox and OD to fit.
Actually the tail of the gearbox sits on a rubber block which is located on the crossmember you will need this for support .
The rubber mount is number C8398 and is called an overdrive buffer costing $16.79 USD.

Your OD tailcase should look something like this item 22. Item 34 is the rubber buffer mentioned by Morris.
There is only one chassis for all XK150. No notch in the center cross member. That cutout would weaken it in torsion, and as a structural engineer I would argue against such a modification.

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Hi Morris and Rob : Thanks for your comments ( and everyone elses). The engine No is V2895-8 and the car was built in Feb 1958 and despatched in Feb 1958 to New York. I see that the O/D sits on a rubber block mounting on the rear of the chassis x member which still exists on my chassis. I have discussed the chassis issue with my restorer who are is a specialist Jaguar Restorer with ex Jaguar people in Coventry, They are satisfied that the chassis as strengthened is OK and the O/D can be supported correctly. Thanks.

Thanks for engine details.
Re the rubber block support, your crossmember does not have enough horizontal support on the top surface of the cross member front to rear for the rubber block, suggest you look into this a little more with measurements of the total length of tranny with O/D.
Good luck

I would be hesitant to trust the opinions of restorers not trained in structural engineering principles on a question like that.
Ask them what is the polar moment of inertia of the modified cross section, using the parallel axis theorem, relative to the original value.


The rubber buffer shoown part #34 is only a buffer ie in normal use it would literally not be in contact with bottom of gearbox it purpose is when you hit a bump the buffer stops undue stress on the 4 engine mounts.

I didn’t understand what rob said but know what he means with that much cut out of centre cross member your chassis is not strong enough.
There is absolutely no reason to cut anything out of an XK140 150 chassis if you are fitting another jaguar box of any type

Sure if you are fitting O/D box in xk120 you need to trim a little bit not that much.
There is something wrong.

Oh , I know this ! , No don’t tell me , just need a little more time , oh , it’s always the way isn’t it ??? Just can’t remember :joy::joy::joy:

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Graham , what’s needed is a lateral shot, rear of the overdrive. If the overdrive shows to be standard 150 has the engine / box been moved rearward?

I am not an engineer, but it is obvious that the cutout made in your cross member seriously compromised the strength of that member. There is no reason not to repair it to original specs now that you have a bare chassis. I would guess that the failure to make the repair would also impact the value of your completed restoration.

I have an XK 140 which also has a transmission and overdrive from a Saloon replacing the original. I did not have to modify the cross member for the overdrive to fit. The only modification required was to shorten the drive for the speedo so the angle drive did not interfere with the chassis cross member. I suspect your 150 is very similar. I agree with Rob that this cutout was probably made (badly) for a non Jaguar transmission. Bottom line, get it fixed now, and don’t settle for anyone saying it is probably good enough as is.

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I’m late to this post, but I’ll still empathize with you as my other '120 had the same exact hack job modification done to its cross member as well with the same type of gearbox. It took me months of pestering others with questions here, sourcing the correct thickness of metal replacement and poring over old pictures to make it right again. Per another thread, only now have I found a taker for the Mark 2 gearbox in exchange for what will be a spare XK gearbox. Best to have your shop make it right again. Good luck.

Here was my mess from 3-4 years ago:

Hi Chris: Thanks for your comments. The gear box ID that was in the car is not the original as doesn’t agree with the ID plate in the car or the Heritage Certificate. However the ID of this gear box is JLS42191JS which I think means it is a 4 speed manual with OD which came from a XK150S - the JS at the end referring to “shaved gears”. So I think it should fit without the cut out in the x - member. I think the cut out in the cross member must have been done in the US to fit some other type of engine/gearbox. The gearbox and overdrive have been rebuilt and restored by specialists in the UK and will be re-installed in the car.


Be aware that the transmission from a saloon will not fit in a 140 unless a 140 top plate is fitted to move the shifter to the required position. This means that the top plate on your car will only show the serial number for the 140 transmission it was taken from. To determine the origin of your transmission, you will need to find the serial number stamped on the transmission housing itself. As shown in the photo I posted above, both the transmission and the overdrive should fit in a 140 chassis as originally configured unless the transmission in your car is incompatible with a 140, in which case I would bail and put in a new 5-speed.