The square plate with the 1/2" fine thread nut in this picture is loose, and the nut or stud one is stripped out. What does this do? I can't get the plate pushed back in either. There are 2 of these on the clutch on opposite sides of each other. [attachment=22235]image.jpg[/attachment]
These 2 locks hold the clutch adjustment ring in place and prevent it turning while the clutch spins. the smooth ring the plates bear on is the adjuster and should screw clockwise to tighten the clutch adjustment so it snaps over center when you pull the lever back. Tighten each one to 30 foot pounds only. (this is for the D69U which has 3/8" studs with 9/16" nuts).
D6 parts book shows a separate stud in each of those locks. Not sure how much success you would have replacing the stud without disassembling the whole thing, but should be worth a try if you could get a stud gripper on it. I believe sometimes they pull out of the back plate, so in that case, could be nearly impossible to fix without removal of clutch.
On the parts breakdown, it appears the inside plate is trapped and cannot fall out, but you could probably clamp a pair of small vise grips on the pin to hold it in place while you remove the stud.
D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time😄