The quadratrac is probably shot. Gotta remember, it's ancient. IF I recall correctly, it uses a clutched cone assembly, which is not uncommon for a worn unit to have the clutch slip, sometimes massively. Also, the chain in these units is prone to slipping, snapping and just flat failure.
1992 YJ, 401 V8, EFI, TH400, Atlas, D60s, Detroits, Warn 8274, Cage, 37 Krawlers
1997 TJ, 350 V8, EFI, TH400, Atlas 4spd, D60s, Detroits, Warn 12000, Cage, 40 Kevlars
TTC 1994, TTC 2012, Trail Tour participant.