Full synchromesh gearbox overdrive rear casing replacement

Hello Everyone,
My overdrive rear casing had been damaged at some point in the past and has been repaired before I got it.
It fits and doesn’t look that bad but I wanted to replace it with a pristine one (which I have bought already)

The engine and gearbox are out of the car at the moment so I was thinking now is the right time to replace that damaged/repaired overdrive rear casing.

I assumed it to be a straightforward job but after I had a quick look at the workshop manual I am not so sure any more: first, there are several overdrives types and apparently the manual doesn’t cover the dismantling of all models (only the compact one if I am not wrong).
Also, it’s not that clear if the casing could be removed directly from the overdrive without letting fall all the internals on the floor in a big pile of gears?!

=> Any experience in removing/replacing this rear casing on the photo? Is it just a matter of removing speedo cable, the casing bolts, and then removing the casing, then replacing the two bearings and refit it?
Or does the whole overdrive need to be dismantled?

Thanks in advance!

Not that my photo helps but I don’t think it’s simple to just remove the rear casing.

I have read a few descriptions of removing the “Laycock De Normanville” overdrives, and there is a number of “tricks” to know on both taking it off and installing it

I suggest you Google search the topic


You would have to dismantle the whole OD. This can be very tricky. Search the XK section, they are the earlier models but will give you an idea of what is involved.

Is your new o\d unit identical to the old? If yes, it’s just a case of unbolting your unit and refitting the new one, making sure to get the plunger of the pump onto the eccentric cam that drives it. There should be a couple of longer studs protruding from the rear of the gearbox to allow you to start taking up the tension of the springs evenly until you can get nuts onto the shorter ones. IIRC, there are 3 sets of splines within the o\d unit that need to be aligned to allow the g\box mainshaft pass through and if you rotate any part of the o\d unit as you offer it up, those splines will misalign and you need to start again. Easiest to do with the gearbox standing vertically. It’s hard to tell from your photo, but I think your o\d unit differs from the original ( is it compact?), and won’t fit because your gearbox mainshaft will be too long. If it is the same, it’s pretty straightforward, but as you fit the o\d unit. press down against the spring tension. It should not strike anything solid, if it does either your splines are misaligned or the pump plunger is not seated properly. Just take your time and don’t force anything.

Do you have an entire OD unit or just the rear casing?

As I understand it, its just the rear casing. an overdrive swap is quite straight forward