In Reply to: Re: AWD vs. 4WD posted by Perry Yantis (Perry) on September 30, 1999 at 14:08:05
: Dave,
: The problem with awd is that 80%/20% stuff.
: If a minivan has this setup then most power still goes to the front axle and the other 20% goes through a torque converter(possible slippage) and maybe get some power to the rear wheels.
I owned an AWD '91 Caravan for quite a few years, here's what I learned. The system has a normal front wheel drive assembly but attached to the transaxle is another drive shaft leading towards the rear of the van. In the mid section of the van is a viscous coupler. This is the unit which is responsible for determining which set of wheels has the most traction, not another torque converter. My understanding is that it is a sealed unit which senses slippage using pressure plates and fluid. It's kind of a black box to me but I know on the Caravan it needed replacing at 105,000 miles. After the coupler comes a torque tube, containing another drive shaft heading rearward, and it connects to the rearend through an overrun clutch. Using this system it is possible to have almost all of the power heading towards the rear wheels, not just 20%.
Living in New England I can verify that the system works. In any snow or ice condition I encountered I never sensed any tire spin. Being a playfull guy, I would often try to spin them, but never could. It just went staight and smooth. Yahoo! Stopping the beast was a different story, Yahoo in a different context. AWD does zero to influence braking, or cornering in my opinion. How the Caravan's system differs from the D, I don't know but I am interested in finding out.
Not quite sure what you mean by torque converter. There isn't an additional converter on the van.
AWD is usually far superior to 4wheel drive in terms of traction. Ever watch those Euro rally cars go? In terms of traction they can't be beat, and they're all AWD.
GB