Overdrive damage means freewheeling transmission?

I picked up a manual transmission with the long overdrive which I ID’d via this forum as a unit from a Mk2. It has the top cover bolted on with 4 nuts.

Is it true when the overdrive fails, that the transmission (car!) freewheels. I.e. direct drive, as in 4th gear, is not going through? And nor are any other gears.

Let me also find a picture.


I’m not an expert but I think it depends on what you mean by fails.

The solenoid allows you to either lock or unlock the planetary gears, giving you either straight through 4th gear (1:1) or an overdrive.

If the solenoid fails and so the overdrive won’t engage it should continue to function as a straight through 1:1.

If on the other hand the planetary gear system fails by virtue of mechanical failure you probably wouldn’t have any drive. And horrible noises.

The Laycock de Normanville units have a reputation of being pretty robust.

G’day, and thank your that feedback. I shall get a cheap Getrag and toy a bit with the adaption, and then decide. I used the short OD version of above transmission in a previous built where I didn’t even check if the OD works. Client can’t be bothered. Our legal top speed is 120 kph.

My mate has 80+ Getrags laying around. If they can be adapted smoothly to Jaguar engines, I am in business. That alone is actually reason enough to discard the Jag box. For R&D reasons.