Jumps out of first gear

Hi Mick,

If you look at the shop on this website, you will find a DVD for £21 dealing with gearbox rebuilding.

Your gears may not be fully engaging and this will cause first to jump out under acceleration. A new spring in the outer cover may solve your problem and it may need a bit of careful bending at the ends to rock the little moon shaped pawl fully into place to do it's job. Quite often the gear lever spindle is rusted undersize and even a new bush will be sloppy.

The inner layshaft bearing used to be replaced by a roller bearing as they were notoriously poor. The latest mod is a deep groove ball bearing. Mick Hemmings sells them I believe

Previously wrote:

Its 25 years since the last rebuilt, but it looks like it is time to strip down my 1972 Commando gear box. The problem is that it jumps out of 1st gear at about 3500-4000 rpm, other than that everything else is perfect, its a really sweet box, no problem with selecting other gears, no roughness, no false neutrals and it does not jump out of 2nd, 3rd or 4th gear.

The external gear shift appears to be pretty sloppy, so I suspect just general wear and tear over the years. I intend to change all of the bushes, bearings, seals etc with the view that everything should be OK when it is put back together.

Has anyone else had any experience of changing the bushes in the castings and covers? is there anything I should be aware of? or is it just a straight forward case of heating the cases, driving out the old and fitting the new?

Any other tips or advice while I have the box apart would be welcome.

Cheers

Mick

Hi Mick,

I had this trouble in the 60's with my Dominator 99 and it was caused by a broken cam-plate plunger spring which can easily be removed on a Dominator without dismantling anything else so it is worth checking out, (I assume that this can also be done on a Commando). After fitting a new spring I lost the sweet gearbox action but had no more jumping out of 1st. gear. This suggests to me that the standard spring is possibly heavier than it needs to be and maybe experimenting with a lighter spring might restore the easy action.

Regards, Rob.

Hi Mick, glad something worked and good to get some feedback as to how you solved your problem.

Hello Mick,

Just passing through the forum looking for something else when I saw your post. I have a 77 MK3 which was jumping out of 1st gear. I noticed that the cam plate action would not engage the dogs more than a third. I replaced the gear because the round engage holes had smeared due to this jumping out of gear action and so far so good. The fact remains though, the cam plate still wont engage the action fully.

Mike

Mike, It sounds to me like the timing of the gear selector arm (the one with the roller in the outer end) and the camplate is wrong. Can you prove that the camplate is being rotated until the plunger makes the detent for each gear. The selector arm can only move so far with the inner cover fitted.