gearbox shell alternative

In respect of the earlier boxes the mountings on the Matchless/AJS AMC gearboxes are in a different place, if they do fit the gearbox will be at a different angle. The internals are pretty much the same if they are the same era. Where is the crack ? Is it repairable?

I think the later boxes were different to the earlier ones and the cases may not interchange, someone else may be able to confirm. Iâd be interested in the pre 65 Norton case if itâs for sale!

The mounting lugs maybe different and need machining back to suit Commando. These old shells will not have the later added thickness of material around the bearings. You will also need to ensure that the inside is proof machined correctly to enable clearance for the Commando gears - should not vary much, but the shell accommodated many gear ratios over the years and fitments, AJS, Matchless, Manx, Commando etc.

You would be best to pick one up with the sleeve gearing bearing in-situ, as this will prove the bearing should not rotate when fit the new bearing.

If you are looking at the eBay ones, itâs the one with an N or NA that were Norton, the M or MA were Matchless/AJS. I donât think machining the Matchless will case help, the mountings are cast in a different place. If you get the Mick Hemings video from the club, he explains the differences and will help with the rebuild!

Andover sell new ones. A bit spendy but it will be right.

Bit late in the day perhaps, but here is a photo which show the difference between Norton and AMC gearbox shells. The AMC box has a serial no. starting with an 'M' which may denote Matchless.

Bob Haslam

Hi Bob,

I have just done this myself. I took an AMC N main case, and fitted it to the 1970 fastback. It had more material than the original gearbox and only required 3.5mm milled of the top mount on the clutch side. The commando uses a 3.5mm washer to compensate the width. They tell me its machine that way to fit into the plates. Regards

Steve

NA case will also do the same job.

Previously steven lewis wrote:

NA case will also do the same job.

Hi Steve,

Glad you've solved the problem. Seems that the AMC 'M' (in my photo) is not the same main casting as the 'N' and 'NA' variants as it is obviously utterly different from the Norton casting.

Regards, Bob