@hammerheadfistpunch what's your take on Jeep's Quadra-Drive II? My WJ had the Vari-Lok differentials and I remember it was quite effective at putting down power in slippy situations.
https://www.allpar.com/threads/the-jeep-grand-cherokee-second-generation-1999-2004-jeep-wj.228758/#post-1085222856
Quadra-Trac II
A new four-wheel drive system, Quadra-Trac II, used a progressive, speed-sensing torque transfer differential - the first industry use of Vari-Lok axles in both the front and rear axle. The Quadra-Drive system kept the vehicle moving even if only one wheel has minimal traction, and worked without straining, wearing or compromising the anti-lock braking system.
Quadra-Drive II was standard with the V-8 and optional on the six (Jeeps made in Austria had Quadra-Drive standard).
The Quadra-Trac II transfer case normally sent most of the power and torque to the rear wheels. The moment a wheel lost traction, a gerotor pump applied hydraulic pressure to a multi-disc clutch pack, sending power to the front axle.
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The gerotor pump used a rotor driven by the front drive shaft and the case by the rear drive shaft, creating a pressurized oil flow to the clutch pack in proportion to their speed variation. Clutch discs were alternately splined to the front and rear drive shafts. Because Quadra-Trac II could immediately pressurize the clutch pack, it had a faster response than a viscous coupling. (Quadra-Trac II's low range had a 2.72:1 torque ratio and fully locked the center differential).
A similar pump was in the Vari-Lok differential; power transfer was proportional to wheel speed difference, rather than torque difference. By avoiding the need to pre-load the differential to assure torque transfer, the Vari-Lok could be virtually wear-free. Vari-Lok differentials responded more quickly and smoothly than viscous-coupling systems, and the pump response could be precisely tuned to driving conditions, enabling the use of this advanced system in the front axle as well as the rear.
