Toyota Highlander Hybrid and Snow

bbb9

Need a good winter car. I'm located in the foothills outside of Denver and snow is possible from Sept to May. I'm thinking about the Highlander Hybrid but wonder how well the auto-4wd really works in the snow.... thoughts or experiences with the hybrid in lots of snow?

On those snow commute days, is there a way to force the Hybrid to run in constant 4wd mode?

Thanks

wwest

I would stay entirely away from ANY FWD or F/awd vehicle as they can turn HAZARDOUS in an instant in slippery road conditions. Much like, and in the same way, as a 4WD/4X4 driven along with the center diff'l remaining locked even with no real need.

There is an indication, a US patent was granted to Ford on this matter, that regen braking on the Escape/Mariner/Tribute hybrids is disabled or reduced substantially if the OAT declines close to or below freezing. The same patent also covers the issue of initially disabling regen the INSTANT ABS detects that a braked wheel is approaching lockup.

IMMHO it would be UNWISE for any FWD or F/awd hybrid manufacturer to NOT follow Ford's lead on this. As an example VW has just developed a new technique to make FWD stick shift vehicles much more safe. VW's technique involves UP-REVVING the engine automatically should a downshift result in front wheel slippage or skidding from the resulting engine compression braking.

ABS cannot prevent or alleviate impending FRONT wheel lockup, wheel skidding, due to engine compression braking, or in the case of hybrids, regen braking. FWD and/or F/awd vehicles are especially prone to loss of directional control on a slippery roadbed for these reasons, most especially so on a slippery downhill.

But to answer that last question for which I have given not a little thought, the only way I can think of is to make the TC system believe the front wheels are losing, have lost, traction with each further depression of the gas pedal. That would mean modifying the signal from each of the front wheel speed sensors. That would take care of putting most of the "pedal-to-the-metal" toward the rear wheels where it naturely belongs. But it would still leave the regen braking at the front and that, as we have seen, can quickly become hazardous in the very conditions for which you want more traction, FWD or F/awd.

The only possibility that I see is to purchase a FWD RX450h and retrofit it with the 2010 RX350's new rear wheel drive setup, PTO and rear driveline clutch. "Hardwire" 12 volts to the rear driveline clutch and remove or disable(***) a front halfshaft. RWD for the times when 4WD is not required but recouple the halfshaft when true "part-time" 4WD is needed.

*** http://www.remcotowing.com/node/7

bbb9

Thanks for the response. I'm confused though.

Are you saying that one should avoid any all-wheel drive vehicle? Or just the hybrid version of AWD given how the hybrid operates?

wwest

It is my position that FWD vehicles are DANGEROUS in the very conditions most people tout them as being advantagous, wintertime adverse roadbed conditions. That also goes for ANY AWD vehicle for which the front wheel drive torque level cannot be moderated.

I consider RWD as being superior to any FWD or F/awd vehicle and R/awd above any of those. The Toyota 4runner for instance. Insofar as F/awd systems are concerned the SH-AWD system is the beat of the best,

bbb9

Thanks. A few more questions.

Do you see any difference in winter handing between the Highlander gas model versus the hybrid?

In FWD cars, isn't front wheel torque a function of current gear and can't one adjust that by shifting? I've got a 5-speed manual FWD and control front wheel spin in winter conditions by putting the car into the right gear for the starting/slowing conditions. The same approach applies to automatics as well, no?

wwest

I would think TC on the FWD hybrid would/could be a bit less intrusive since drive torque is more easily moderated/modulated. If Toyota wanted the AWD HH to be R/awd in times of need, adverse conditions, it certainly could be.

The primary problem, safety issue, with FWD is encountering a slippery section of roadbed inadvertently, unknowingly, (or maybe just blissfully ignorant of conditions) and then having to recover AFTER the fact. Having a FWD with a clutch is certainly an advantage but those were/are being discontinued right and left.

Perhaps now that VW has come up with a technique to make manual FWD's more safe that trend will reverse.