3325 winch seems to be slipping.

[Cuzz]

Just got around to putting the (well used) winch on the 450c dozer.

Removed clutches and cleaned them as they looked as if they had been packed with grease. Removed and cleaned brake band. Lots of oil in the compartment. All cleaned, dried and put back together. Brake hydraulics seem to be dry. Pressure plate swivel had a very slight leak but I put new O-Rings in and stopped that.

Winch pressure -
600 lbs. at 1000 rpm
1100 lbs. at 1400 rpm

New hydraulic filter

Cleaned snot off of the hydraulic pick up (looked really packed in)

Spooled up the winch with 100ft of 5/8 cable while pulling my Kubota rubber tired backhoe for resistance on level ground. The last wraps on the full drum I really had to rev the motor in order to pull in. Acting like it is clutches slipping. The clutches looked worn to me but I'm not sure to what point they become non functional because of wear.

What can be causing my apparent lose of winching power?

Is there a measurement for telling condition of the clutches?