Only two gears

Sounds like you could be a tooth out on the quadrant. Been there ,done that a couple of times. Very character building !!

I think that as you were able to obtain 4 gears by using a spanner on the Quadrant nut then I am going to put my bet on the thin Gearchange Spring either being upside down or out of position.

This spring can be a real pain, in the AMC gearbox, as in order to work correctly it must have the correct shape and just touch the floating crescent shaped selector pawl.  See attachment.

Old Britts do a good Commando gearbox but its still an AMC box, 7/8's down for the spring info.

https://www.oldbritts.com/gearbox_a.html

I have always spent time to ensure the smallest possible clearance between pawl and spring arms, and buy a few springs from different sources to have a selection to work with. All have needed some light bending with 2 pairs of pliers.

My advice is forget about Haynes and get a copy of the Mick Hemings video from the club! I also expect it’s the spring.

dan

Where are you Roger?. There may be a Magician somewhere local.

Roger......The fact that you are able to select all 4 gears using the Quadrant nut strongly suggests the problem lies in the gear change / selector region. Generally this is due to an issue with the selector spring but a broken return spring would also stop some of the gears from getting selected.

The return spring is almost immediately belhind the selector spring and returns the selector pawl back to the neutral position. See attachment which shows the 2 springs from the inside looking towards the outer cover.

If this section of the gearbox has not been correctly assembled then the return spring can get wedged open by the large washer that holds it in place. Especially if the large washer has been replaced by a much thicker item. The same problem will happen if the spring is cracked or broken.

The selector spring must be exactly the right shape so that it just touches the sides of the pawl. while each leg passes through the slots of the bracket.

The second attachment shows a bundle of gearbox springs sold to me as suitable for an AMC gearbox. More than half would probably not work.

Roger.......you should be able to both see and access the quadrant and camplate nuts from underneath..A cranked ring spanner on the camplate nut will probably be the easiest to turn.

See photos of Commando gearbox diagram and my gearbox in frame. The 650 and Commando gearboxes share many components.

Have you put the gear lever back on the shaft of the outer cover alone and then operated the lever. I have and if the pawl spring is not right you can see the pawl not move enough to engage with the mating teeth on the ratchet plate. 

The most obvious nearby NOC support would be a member of the Bournemouth Branch.

Further east and you are inside Solent Branch territory.

If you have very deep pockets then north of you is Norman White.

Which part of East Dorset are you residing in?

Do these help?

These are from the later manual.

Dave.....everything you have posted is exactly what I do. The quadrant roller /knuckle is set at near the top of the slot. Possibly for a reversed gearchange or Mk 3 Commando the settings change.

Roger has stated above that he only removed the outer cover so the quadrant and camplate should not have changed. He also mentioned the gearbox all worked fine before he removed the outer.

Logically the problem lies with the gear selector.  His description a few postings above seem to support this as he mentions being able to obtain two gear changes. This indicates a problem with the half-moon quadrant (pawl) not operating the gearchange rachet. This is generally due to the spring not being the correct shape or wrongly positioned. But........

....another possibility is the rachet pin not engaging with the hole in the quadrant knuckle roller when the outer cover is replaced. Instead, it is sitting above or below the roller and thus only pushing in one direction andthereby only allowing selection of 2 gears. This would fit in with Roger's description of limited movement of the lever in one direction and something solid in the other.      See the Mick Hemmings attachment for pictorial views of chunks mentioned.

That's what I'd do.  It's not very difficult (unless there's lots of sealant involved!)  The lever has to be fitted properly before the cover goes on.

Dear Roger, been there myself, many years ago.

It is possible to select all gears with quadrant one tooth out, by levering it up and down, but it won't work using normal mechanism.

Sounds like you need to experiment a little. Remove outer cover, undo fixings on inner including nut on mainshaft, holding quadrant wiggle case out a little till you can drop outer part of quadrant a tooth ( inner end goes up a tooth) then put on a couple of nuts, and add end case with a couple of screws. I think you will be put out of your misery! If it now selects all four gears you can do proper assembly job.

If you need to pull inner cover to seal it have a very good look at positions and photograph them.

Hope this suggestion helps and provides a way forward, should only take half an hour.

Regards Martin

I can recommend the Clubs Mick Hemings gearbox video , it explains it all very well.

Dan