955 traxcavator over center clutch not staying engaged

I have a recently purchased 955 traxcavator and the clutch will not stay engaged it doesn't snap like it's supposed to and after working it awhile it stops moving and wants to make a gringing noise in all of the gears forward and reverse. I've tried making adjustments I adjusted the disk itself where you lossen the two tabs and rotate the ring I've tried adjustments just the clutch without the clutch brake hooked up tried all types of way but can get it to snap into place, the man I bought it from says it worked then stopped at some point. What is it the makes it snap into place what part, is it part of he clutch or transmission, what would be wore out that keeps it from working properly,  could I just have things over adjusted? The lever doesn't seem to have much travel the pad on the clutch brake is pretty wore I have it adjusted like the book says. With certain adjustments something's work better and some don't but I'm a bit confused on which at the moment. Thanks for any help or advice in advance, I really need to be using this machine now I've done lots of work so far and this is all that's keeping me from making money with it. Thanks again.

is there adjustment on the link rod from clutch lever to clutch arm. if that is right it might be a problem. take the clutch inspection cover off and run the machine observe what happens.
i know with the d4 u series it should be around 75lbs of pull force to engage the clutch. other models i dont know. get a spring scale and check the force needed.

you should have 35 pounds on cluch lever for good adjustement and for adjustement you need to turning clockwise 3 inchs and lock the nuts

Thank you for your reply, that's what I done it was about three inches and it was getting tight at that point. Could I have over tightened it?

okay i was a bit off. it should nicely snap over and stay there till you release it.