Gear selection problems

Hi Martin. You might not have to remove the box but you might need a certain amount of stripping down. It is strange that the change down from third to second is influenced by the fact that fourth has been selected previously. You would imagine that once you were in third gear the change would the samewhatever the previous gear had been unless of course the selectors have not been moved far enough from fourth to third. So although you are in third gear from fourth gear, you are only partially meshed in third gearand the changedown to second gear now has further to move.If you only go upas far as third and then back to second, the selector might have an easier job moving it. My first suspicion would be that you are just one tooth out on the quadrant, probably with the knuckleset too high up for fourth gear, but could the other way although I think this would make first gear selection difficult.

I did notice on my last gearbox rebuild for the Laydown type, (very similar internally) the cam selector forks, although they are identical, I noticed that one had its cam-plate pin ground off slightly. This was obviously done by the factory. After examination I realised that it was the selector fork nearest the end cover that required the shorter pin version. The reason being was that the cam plate is very near to the quadrant lever and when the cam plate revolves, there is a point that the arm of the quadrant lever sweeps past the selector fork pin that,if too long, will protude past the rear of the cam plateand make contact with the lever as it is moved up and down.

This might have been a manufacturing problem but the selector fork pins in my case were different lengthsand if reversed would have caused a selctor problem. This is probably not the case with your box, but if all else fails it is a possibility.

Otherwise I do not know, but hopefully someone might have had the very same problem at one time and will know for sure what is wrong. I am forced to ask and I know it sounds a stupid question but you do have oil in the box? Not trying to be funny but it would be easy to forget.

Les

I struck the same problem on my es2. I replaced the bushes for the quadrant and the camshaft,and gear changing became very stiff with a bar inserted into the fork end of the quadrant to test the box, without the detent spring.I looked inside the box and could see the peg of the selector fork fouling the quadrant as it crossed it.I had left the bush slightly proud of the casing inside, because I couldnt be bothered pulling it back and filing it.The other thing of course is not to over tension the detent plunger, and jam it into the cam notches.As Leslie, peter says one fork is often ground on the peg and thats what I did to get clearance.Regards John.

So glad you raised this Martin - just completed rebuild of my AMC type gearbox N11127 and despite careful checking/experimenting with "knuckle" to quadrant positioning have identical issues as yourself. For some reason gears index perfectly using the camplate only (i.e. without the ratchet assembly) which initially led me to thinking that the ratchet-to-pawl relationship was somewhat dodgy for the downchange direction. Looked and can find nothing amiss - can only surmise that there's some kind of lost motion which is occurring when shifting duties are tranferred to the ratchet plate assembly.

I'm going to have a look at "timing" again to see if it is possible to improve the knuckle positioning. If no joy I'll take a look at how far the selector fork pegs project into their respective camplate tracks.

I suggest that you check out both of the springs inside the outer cover that effect the gear changes. The larger item called the Gearchange Return Spring tend to crack on the rounded shoulder. Quite often allowing easy gearchanges inone direction but not in the other.

The problem with this spring is that, in situ, it usually looks ok. YouReally need toremove it from the cover for a good examination. When replacing this spring, check to see that it is correctly sited and don't forget the large washer that sits over it.

The other problem area could be the Rachet Spring. It is very easy to insert this item the wrong way round. This then causes problems with the rachet mechanism failing to engage properly and move the gears. The correct version of this spring hasone long straight arm. The other arm has a kink in it. The kinked leg mustsit at the bottom. See attachment.

Beware of cheap versions of this spring. They either do not have the correct shape, kink or tension and will not function correctly.