AMC Gearbox Identification

Previously dave_taylor wrote:

I've been clearing out the garage and came across an AMC gearbox M29830R. Has anyone got an idea of what model it is off?

Regards,

Dave

hello that depends were the cam plate is or which end of the box is at Matchless boxes the cam plate that the rear end next to the tyre so matchless boxeswere close to the engine Nortonbox cam plate up the front end next to the engine but farther away from the engine, hope this puts some light on things yours anna j

Dave. I understand that an AMC gearbox with a M prefix to thenumberss either for a Matchless as Anna J has already mentioned, and/or for a AJS model.

Regards

John S

Most likely off a Matchless G12CSR or AJS31CSR as the R stands for close ratio.

Paul

Can you tell me anything about the close ratios in a R gearbox?

Paul

Previously paul_nicholls wrote:

Most likely off a Matchless G12CSR or AJS31CSR as the R stands for close ratio.

Paul

If I could jump on this thread please?

Trying to identify my AMC gearbox which has N1582 stampede on it, looking for model and age if possible?

Thank you

The change-over to the AMC gearbox began in April 1956 but only for some bikes as the batches supplied were insufficient to match weekly production rates.  The very first batch of 88 and 99 models fitted with such being only 67 in total. Roughly just a third of a normal weeks production.

These gearboxes were allocated to bikes with engine/frame numbers 68761 to 68828. From then on old stocks of the ‘lay-down’ box were fitted to the next 101 bikes.

Once fresh supplies of the AMC 1 began to arrived more regularly, from bike 68931 onwards all the Factory production of the late 1950s Models 88, 99 77 and then Nomads had AMC 1 boxes fitted as standard.

My date guess for Gearbox N1582 being that it was fitted to a 1956 late summer production Norton.

Dave...if you have both boxes you can obviously try them. The big changes were from lay down to AMC. Even then the layshaft first gear fits from Doll's head to Commando. 2nd and 3rd changed from 4 dogs to 3 when AMC box appeared. 4th changed quite considerably. Sleeve gears etc changed lots of times, as did kick starts.

It would be great if somewhere in the tech files there was a comprehensive list of which gears can go where. Some can be moved from early Doll's Head to late AMC provided they are swapped together (e.g. 2 and 3, so the numbers of dogs match).  First main shaft gear has a boss on AMC which must be turned off on a lathe to fit Doll's Head.

But the Doll's Head became the Tombstone and then Laydown and I think (please correct me if I'm wrong) that those three all had interchangeable internals. Some even swap with the Sturmey Archer 4 speed. Don't know about kick-start or sleeve gears. 

RGM sell some early box gears but not all.

Do you want close ratio especially? Since you have a wider torque range than a racing single, won't a wider ratio make it more fun on the road?