Jumping out of first gear in the AMC box

This is probably a camplate issue causing the second dog gear to drop out of engagement with the first gear. It is possibly just one tooth out of sync. The bad news being a gearbox strip to correct.

Previously tom_mcewen wrote:

Can I do that with the gearbox in the frame?

Yes...........you will have to remove the inner cover to get at where the camplate is hiding. This means removing the actuator arm and mainshaft nut which is hiding under that chunk. Plus the 7 nuts which hold the inner in position.

Unscrew the rod that holds the selector arms. This has an 8mm flat on its end. The selector pins can then be lifted clear of the camplate and away from the gears they move.

To make space inside pull off the first two mainshaft gears and three on the layshaft. Try not to mix the gears up.

The external camplate nut will need to be released so that the plate can be lifted to make an adjustment. It is probably just one tooth out of synch.

Before bolting everything back together stick all the innards back in place including the inner cover and test the gear movement. Use the other external nut for the gearchange quadrant to move the gears.

The two hardest parts of an in-frame rebuild are ;-

1) Getting the selector arms back in place. Gravity tends to pull the pins out of the camplate when screwing the pin in place. Use a long thin screwdriver to lift the arms a few mm to help line the rod up with its hole.

2) Getting the outer cover gear change shaft back in position. Again a thin rod may help to nudge bits into the correct place.

Attached are a few useful pages.