4. what is wrong with transmision/torq-conv on my Jcb 3cx 2 wheel dr.1981?

Hello
It would be normal to allow a small amount of free play in the linkage, ie. a small amount of movement in the pedal before the plunger moves.
Unfortunately, you now seem to have checked and ruled out the easy options. I am sorry, but it is looking as though you have a g/box problem, which is something I can't advise on - have never had cause to go inside one.
You might try giving Lee Gregory a call. Search for "Digger Doctor" for phone no./email. He will probably advise and can supply s/hand parts for these older m/c's if necessary.
Sorry I can't help futher!

Apologetic Mr. Toad
May 2009