Eaton winch brake slipping on 230TJ

[Mountain_d]

I was hoping some members can help me out. I have a 1978 TJ230 with Eaton winch. The brake is not holding the load up as it should. It was slipping a few months back and I adjusted the two jam nuts on the cylinder and that helped but it is slipping again. My bottom nut only has about 2/3 of the nut threads still on the bolt and the top nut is snugged up so I figure I am out of adjustment. I thought the break banks were worn but I can see through the inspection hole in the winch guard that I have about 3/8 inch of friction material on the band. Could it be that my spring inside the winch cylinder is weak? How likely is that? Can anyone suggest other likely causes? 
Thank you all. 
Mountain D

[Mountain_d]

I can also add that there is no oil leaks so the slip is not caused by oil on the friction material. I believe it is the spring inside the cylinder that holds the load up and when the hydraulic piston is pressurized it overrides the spring and allows the load to drop. Is that correct? 
Mountain D

[fluidpowerpro]

Might want to check the drain line from the brake. If for some reason your back pressure went up the brake will be partially released.