AMC gearbox problem

Previously colin_ansell wrote:

Another gearbox problem looking for a solution;

Ihave rebuilt my box using both the Mick Hemmings article and the Old Brits website info. Howver, I cannot select any gears or, at best, can make only one change (eg from 2nd into neutral but then nothing more).

I have searched the web and read all of the NOC articles but no joy. I am absolutely sure timing is correct and if, with the cover removed, I fit the ratchet I can select each gear (and neutral) with no problem. I have checked the (new) hairspring and it is fitted the correct way round (bent leg to the bottom) and there is just a small clearance between it and each side of the pawl (and the pawl rotates freely)

What I have noticed is that with the gearchange assembled into the outer cover, there seems to be limited gearlever movement. It almost seems as though the return spring is somehow restricting how far the pawl carrier can rotate - I have compared it with another cover and that seems to have a much greater range of rotation. The carrier moves to each end of the slot in the stop plate if the spring is removed.

So, I think that the carrier doesn't rotate sufficiently to allow the pawl to engage with the ratchet.

I have spoken with the (reputable) supplier of the spring and he is not aware of any issues with them.

any ideas?

Thanks

Colin

did you select second gear before replacing the outer cover, !!!

Check all of the springs in the outer section. There are several possible causes for non-selection because of problems with these items.

First I would look at the big chunky one that keeps the selector arm central. These can split but appear ok. The result is no gear changes after one push of the lever. It is a pain to pull out of the cover to look at but is always first on my check list of a gearbox that will not select.

Secondly. The thin selector spring with the kink has to be exactly the right shape or it will not do its job properly. There are lots of copies of these on the market and fitting a cheapo one can be a waste of time. Also it must be the fitted correctly with the straight leg at the top....Why I just do not know?

Third. If the gearbox does not select gears when using a spanner on the outside camplate bolt then I would be checking the plate for a mistake during assembly.

Attachments illustrates the point I was making above about the big variations you can get with these springs. The kinked leg, in the selector spring, is critcial for the gearbox to work correctly. Only one out of that group of five actually allowed a full selection.

The big selector arm return springs are equally different in style plus, as I mentioned, if this one cracks you become roadsided very quickly.

A very important point I forgot to mention was the big washer that sits behind theselector arm return spring. It has to be there and must be the correct size. Different thicknesses or diameters of this item will also cause that spring to stop doing its job properly.

Pic with spring measurements is somewhere else in this thread.

Phil's advice is all spot-on. There is some obscure black magic that goes on inside AMC gearbox covers and it can't be explained by conventional engineering or physics...

Have you seen this thread on Access Norton ? Apparently there are even different spring stop plates and some cause more problems that others...

http://www.accessnorton.com/gearchange-problem-solved-t16826.html?hilit=pawl%20plate#p208355

The washer that Phil mentioned is indeed very important. If placed the wrong side, it causes no end of problems and yet it's something that doesn't have an obvious function.

Attachments are from Mick H gearbox rebuild. They show the BIG washer sitting between the springs presumably acting as a separator.