Mk5 Overdrive Conversion

Hi everyone, there have been a few questions around the overdrive fitment I did to my Mk5.

My priority was to keep the car as standard as possible, and the only issue I was concerned about was cruising speed, and the limitations of the low-revving pushrod engine combined with 4 speed gearbox.

Fitting an overdrive means you can retain your original car gearbox, I was not prepared to start fitting a different gearbox from other cars. You need a donor moss box with overdrive. Our mk5 gearbox was in excellent condition, with no gear or synchro wear apparent. Therefore, we stripped the donor mk7M/mk8 gearbox, so we could use the longer main shaft. We stripped the mk5 gearbox, and re-assembled using the longer main shaft, and then the overdrive just bolts onto the rear.

I will try and take some pics this weekend, as ironically we have had some oil pressure issues with the overdrive, I have done 1,000 miles of running in, so am now doing the first major service. The oil pressure issue has been identified as the O ring seals we fitted to the accumulator piston - within 1,000 miles the new seals have shrunk! Cheap chinese rubbish from a reputable bearing supplier. We managed to locate some high temperature O rings, not easy as its a size that is not commonly utilised in any other applications.

Fantastic! Thank you so much for doing this. I’m really looking forward to seeing what you have done including the wiring as well as the switch on the dashboard.


Same here. I’ll be yanking the engine today to have the rod journals ground and clean everything. It would be the perfect time to upgrade the tranny.


I borrowed a J type Laycock OD and was trying to find a place under north to remotely set it. I was told by a Laycock rebuilding shop that only the A will fit the MK V. Would have to swap main shafts in the tranny and all said would be about $2800 which is more then I want to spend to increase speed by 25-28% .
I was hoping to mount it after the center bearing but I don’t think there’s enough room for suspension jumps. Attaching it to the pumpkin has its own draw backs. Now I’m considering swapping the tranny for a Volvo with the OD already connected. I’d have to change the clutch plate or change the spline one this one. Plus adapt a bracket for the starter motor but it’s another possible route.
Has any one here successfully adapted a J type to a MK V?

Here is a picture of a box from an XK140 with a serial number beginning JLE.

Here is one which I think is from a Mark VII, can’t tell from this angle. If so, it would have a serial number beginning JLN.
OD trans Mk7 or 140

Either of these would fit your Mark V bell housing, no need to swap the mainshaft.
Whether or not they would fit in the chassis, I don’t know, but I have my doubts. Certainly you would have to engineer up some sort of a strong rear mount.

Certainly looks like the X frame would need massive modification: not a trivial task.

At this point, I’m just casting about to see what might work.
Today I removed the tranny, clutch and flywheel in order to get the crank out. Need to have the rod journals ground to fit new big end rod bearings and instal the pistons. I found that the spline in the clutch plate fits a Volvo tranny shaft and the complete tranny with J type OD is within 1/2” in length of the original tranny. If I can make a mounting plate to mate this to the bell housing, it might be a solution to the OD problem.
On another note, I’m finding that the engine has black paint over a greenish blue paint with no other color below that. I’m even finding it under the end plates and in places that haven’t been touched in a long time if at all before. Seems there wasn’t much care taken in prepping the blue paint before painting the black as the two colors have separated in a lot of places. It just makes me wonder how many times this engine has been opened.

I agree. You remember the discussion we had about the rear gearbox mount, the sandwich type vs the spindle type?

Perhaps it could be modified to suit?

Nevertheless, I’m really keen to see how the overdrive has been fitted successfully.


I would be interested to know if this would be an achievable modification for the Mk IV. Noting the need to devise a suitable rear mount, does the tunnel need modifying too? What would be nice would be to have the later '60s era all-synchro box with O/D.


Early E Types has the double spindle style of rear mount… worked fine.

Have you been able to take some photo’s as I’m still really keen to see what you have managed to achieve.


I made the adapter plate and it all looks fine. The end result is a 3/4” longer unit from the front of the bell housing to the end of the propeller shaft flange. I’ve yet to tray and put it in the car because I’m in the “painting portion of the program”. Changing the car from dark Blue with turquoise interior to Black with tan leather. The turquoise leather was falling apart and the color just really hurt my eyes!
I’ll post photos of the engine/tranny once the engine work is done and it’s ready to go back in the car.

Thanks for that, Wayne. I’ll look forward to the photos!

Turquoise is a very odd colour but no doubt appealed to people in the 1950’s? I’ve always liked a really Dark Blue with Deep Red interior but colours are very personal. Ever considered a two-tone? Mine is Black over Cream but Black over Red is nice. This one is quite lovely.


Nice colors but I’m going a bit more subdued. This is what I’m after. image


I don’t think anything like that was available originally, but perhaps to some eyes the “Suede Green” once it had faded 30-50 years or my car’s original “Pale Blue” interior might have looked somewhat “turquoise” to some eyes. Or then it’s been rodded before. :smiley:

For MKV in 1949-1951 ONLY these interior colours were available from the factory:

  • Biscuit, Connolly VM.3234 (Connolly called it “Beige”)
  • Grey, Connolly VM.3230
  • Pale Blue, Connolly VM.3244, Jaguar later called this “Light Blue” although most would agree it looks like grey, but it’s more “blue” than VM.3230 called “Grey”, thus “Pale Blue”: :slight_smile:
  • Pigskin Grain (Tan) same tone as Connolly VM.3280
  • Red, Connolly VM.3171
  • Suede Green, Connolly VM. 3510
  • Tan, Connolly VM.3280

Black, Connolly VM.8500 (no sample provided in the sample booklet) very rare and not standard on any MKV, later in XK’s it was used more.

Dark Blue, Connolly VM.3197 was only used on XK’s with the “duo-tone” interiors called “Light and Dark Blue” together with the “Light Blue / Pale Blue” Connolly VM.3244.

FWIW the Jaguar “Tan” is the same tone as “Pigskin” aka “Pigskin Grain Tan” and in some cultures would be described as “Tobacco” or “Cognac” etc. a very saturated brown, like the American football (which is not a ball IMHO ).


The ‘white-walls’ really suit the MKV and maybe the MKVII’s, MKVIII’ & MKIX’s but no other Jag’s IMHO.

My 16 year old daughter describes the all Black car as a “Funeral Director’s car”. I’m very happy with my Black and Rolls Royce Ivory version. Queen Victoria had this combination and Lady Felicia from Foyle’s War has a RR with the same ‘split’.




I must say I really like the all black car in your first photo but is that a priest giving it the last rights?

Peter :wink:


She may well be! :innocent:


Nice! But the nave plates (hub caps) were not Black! They should have been. :smiley:


PS. This is how the world changes, almiost ALL big large saloons, English, American, German were SUPPOSED to be Black in the 1950’s, and they were mostly driven by a chauffeur, even here in Finland, but as Bob put it, The Times They Are A-Changin’.

Here’s a pic from ca 1955 in Helsinki, both car ID and owner ID unknown

It could have been #527062 (Delivered new in Helsinki in 1949 Black / Red) or #627256
or #627286 (both delivered in 1949, at least one of them in Helsinki and both Black / Red) but most likely not #627739 which was delivered and displayed in the Jaguar launch event in Helsinki in February 1950 together with #670057 and #527105 (Lavender Grey / Blue), as #627739 was Black / Biscuit and the light interior would be seen in that photo.

Here is #527105 (Lavender Grey / Pale Blue) again, this shot has been with false info in some books, the original one is in the Bealieu archives. Unfortunately that car is lost, #627256 exists as a project (for decades already.)

And they were subsequently.

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