Gearbox jammed

Should be straightforward to find source of problem. Have you tried levering the quadrant up and down with the cover off? A large lever between quadrant and the opening works well. It will be relatively stiff to move but should do so. If not either the bushes are overtight (have to be reamed I think) or something is causing these parts to jam.Tightness of the main quadrant and camplate bolts is important of course but since the shafts are longer than the bushes there will be end play there and therefore should be no binding. Camplate should not be stopping the quadrant from rotating either and while I don't think it possible maybe if the bushes are not in to same depth or not in far enough I suppose it could cause the quad or plate to jam against the inside of the box. Can we assume the camplate plunger is free in its housing?If that's all ok the problem could be in the outer cover. Does the selector ratchet move up and down freely? Sometimes it can bind/drag on the support plate groove but not usually enough to cause a jam.

You dont say what you used as a rebuild guide but have you seen the Old Brits tech guide on gearbox function and rebuild?

Let us know how you get on......

You may want to have a look at this thread (under Heavy Twin messages);

I had what sounds like a very similar problem - essentially the gearlever return spring was winding up on the outer cover boss thereby restricting movement. It is a good idea to operate the gearlever with the outer cover removed and check that the pawl is able to move the full travel of the slot in the plate.

Mick Hemmings confirmed that there are many small variations in these apparently identical gearboxes and so the parts are not necessarily fully interchangeable.

Previously andy_withers wrote:

Thanks for the feedback on this gearbox now working fine. Old Brits Tech Guide great. Thanks

What was it then?