Combines 8820 walkers slowing down

soon after I got my 7720, I tightened the bolts holding the wood blocks on the back of the walkers. I overtightened them and the walker clutch started to slip. don't know if this will help, but a possibility.

the walker runs off of the counter shaft however what runs the countershaft, better check further back down the line.

assuming your cranks, wood blocks and walkers are ok, the problem is with the length of the bushing in the clutch, trim 1_8" of all four bushings, this problem has been more common as the machines are aging, hope this will help.