| The steel drive plates will stress relieve because of heat over time. This can cause glazing and some warpage. Clutch dust build up will also contribute to chatter, groaning and slippage. I suggest disassembling your clutch pack, lightly sand the steel plates and clean out the clutch area. Measure the plate thicknesses to verify that they aren't worn out of spec. This should help for a while but the symptoms will likely reoccure in time. Just the nature of dry clutches. | 
Threaded Mode