Jumping out of third gear

[k.russell]

spc type 9gearbox annoyingly keeps jumping out of third gear only, mostly on down change, otherwise great gearbox, spoke to Steve and he suggested stretching the detent spring in the top left hand side case, behind 10 mm Allen grub screw. This has improved the problem slightly, I stretched around 3-4 mm as it was quite difficult. Anyone else had similar problem or can anyone explain how this all works. Will speak to Steve again for suggestions. Any info please.

[Birkin S3 ZA.]

It sounds like you need to replace the 3rd/4th synchroniser unit and 3rd gear as this has the teeth for your synchroniser to engage onto with the brass synchro in between the two.

If its been grating the gears the teeth will be worn causing it to jump out of gear.

Some of the parts will have to come from another box as there is no new parts available.

Chris.

[Mankee]

Is it one of Steve's gear sets in your box? I think the actual gear and syncro hubs are pretty tough. The standard brass syncro rings are much weaker but cheaply available. These can shatter if hammered.

 

It might be that the blocker bars and/or syncro hub springs have failed or become dislodged, causing the popping out of gear, as there's nothing providing spring pressure to keep the hub locked onto the gear. There's one wire spring each side of the hub, so that might explain why 4th is OK.

 

In my spare gearbox, I found bits of mashed up blocker bar stuck to the magnet at the bottom of the box when I stripped it down. As well as a broken 2nd syncro ring. It'd been pretty roughly shifted!

[Nigel Riches]

If SPC come up blank on this, a wide range of Type nine spares are available here.

www.bearingkits.co.uk

Nigel.