Moss box synchromesh

[Allrand]

There have been many posts/comments about poor synchromesh in Moss boxes.

During the lifelong restoration of my '64 3.8 fhc I stripped the Moss box to ascertain it's condition.

Having driven it initially many years ago there was little or no synchro action.

The internals were in remarkably good condition, with still well defines groves on the synchro cones, the only ware evident was on the lay shaft just starting to break through the hardening. The shaft was replaced together with new needle rollers.

Something I've never seen referred to in any posts is the synchro throw over detent pressure. According to the workshop manual the throw over pressure should be 62lb. I measured mine e few times by simply pressing on a bathroom scale till throw over occurred, mine were both only around 42lb. According to the manual this can be adjusted by placing spacers below the detent springs. I inserted small 1mm thick washers below the springs & re-assembled. This was sufficient to restore throw over pressure to 62lb.

I've only recently (almost) completed restoration and only driven around the block a few times (because it's not road legal yet) but already there is a vast improvement in synchro action compared to what I remember it being before.

Will update once I've got it legally on the Road.

[PeterCrespin]

Interesting - but presumably unconnected to the graunchy first/second change (in either direction) that you have to 'learn your way around'? I never found the others too bad. I must also say that the two LHD Moss box cars I drove were better for selecting first from stationary rather than reverse. That was the real nuisance for me in my RHD Mk2, because the (selector rod) detent was weak and it was a fine art to be certain you hadn't over-reached and were about to reverse briskly into the car behind...

[abowie]

I rebuilt a Moss box recently and used 1/16" thick washers under the springs. I like your idea of using the scales.

You can actually buy the detent springs; C900 for 65p each.

I haven't actually driven the box though....

[Allrand]

I've had many BMC products and Jags over the years with crash 1st gear boxes. I found out long ago that at dead stop simply moving the gear lever towards 2nd gear until I feel slight pressure on the synchro and then straight up into 1st will select 1st without crunching, no need to fully engage 2nd and no need to double de-clutch. This still works perfectly on my '51 Mk 7 Moss box (which still has acceptable synchro action but don't rush it!).

I don't try engaging 1st on the move, these cars have plenty of torque to pull away in 2nd if still on the move.