As mentioned in yesterdays post, the overdrive was jumping out of gear under hard acceleration. Bearing in mind the engine is, in effect, brand new and not run in, “hard” is a relative term.

But the fact remains, the lever pops out with a tremendous “BANG” and drive is lost. Not ideal…

Series land rover gearboxes have a habit of jumping out of 3rd gear on overrun (going down hill with feet off the pedals). This is mainly down to either excessive wear in the layshaft gears or a poorly adjust selector. The overdrive is brand new so wear isn’t an issue and there is nothing to adjust… except one thing.

A quick Google and the solution presented itself and re-read of the installation manual confirmed the following: (wish I’d read this yesterday)

The detent spring that holds the selector shaft in the “out” position sometimes needs to be stiffened up a bit.

By way of explanation, I’ve marked up the cross section through the overdrive below. (Ignore the black and white numbers)

  1. The detent spring presses onto…
  2. the 3/8″ steel ball bearing, which in turn is forced into…
  3. the groove on the selector shaft; stopping the shaft moving involuntarily backwards and forwards. (The gear lever is attached by way of the linkage to the end of the shaft.)
  4. To increase the rating (stiffness) of the spring, washers are inserted behind the spring.




First of all, the linkage needs to be removed to get access to the machined block housing the detent spring


The removed linkage is held out of the way by a trusty Christophe toe strap. Now the block can clearly be seen. There are two allen key bolts on the underside that need to be removed.


Block, spring, seal and allen bolts. The hole where the spring sits will house the washers, under the spring.


But…. maybe I have a longer detent spring. There are 2 in the main gearbox top cover (see below) and I found an old one I’d take off during the rebuild (top left). But it’s a bit on the long side. 3 washers were measured up instead. This made the spring 2.78mm longer but I found it was almost impossible to shift the lever. So i went with 2 washers (1.77mm).

It’s not a very scientific fix but then again, it is a Land Rover…

The vehicle no longer jumps out of gear, so i’d call that a success 🙂

Main box detent springs…