Sorry I missed this....
Rich has this right, the VC is a VC, it's design is so that the ABS can function in low tractive conditions. The HF2AV is referred to as a viscous coupling differential lock. It is a driveshaft speed differential device (turning can fool it, but that's not it's intended lockup design). It can vary torque between axles at ratios up to lockup (called humping) but is designed to be around 4:1 in most applications.
It's removal won't yield you 1 mpg, and taking it out only makes non locked diff mode less effective under low-cf braking.
You can convert the rotation difference to degrees, the tight VC's (as the 80 is) usually has begun lockup within 45degrees of driveshaft rotational differences.
These HF2AV type differential locks are found on less than a handful of production vehicles, and is a credit to toyota for actually having 4 differentials on a 3 diff awd system.
ID, I suppose under turning more torque is sent to the rear wheels allieviating some of the understeer, but I don't believe that was the intended design. Audi went from lockers to torsen for the same reason, the market demanded passive AWD LSD *and* ABS function, and both the VC and the Torsen deliver that.
HTH
Scott Justusson
landtank said:these threads aren't the same without Sumotoy.
Rich has this right, the VC is a VC, it's design is so that the ABS can function in low tractive conditions. The HF2AV is referred to as a viscous coupling differential lock. It is a driveshaft speed differential device (turning can fool it, but that's not it's intended lockup design). It can vary torque between axles at ratios up to lockup (called humping) but is designed to be around 4:1 in most applications.
It's removal won't yield you 1 mpg, and taking it out only makes non locked diff mode less effective under low-cf braking.
You can convert the rotation difference to degrees, the tight VC's (as the 80 is) usually has begun lockup within 45degrees of driveshaft rotational differences.
These HF2AV type differential locks are found on less than a handful of production vehicles, and is a credit to toyota for actually having 4 differentials on a 3 diff awd system.
ID, I suppose under turning more torque is sent to the rear wheels allieviating some of the understeer, but I don't believe that was the intended design. Audi went from lockers to torsen for the same reason, the market demanded passive AWD LSD *and* ABS function, and both the VC and the Torsen deliver that.
HTH
Scott Justusson
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