truck and trailer total loss due to black ice

Cdash wrote:

Coach-man wrote:


As far as the Four wheel drive issue. Older four wheel drive you should not. Drive on dry paved roads. As explained, in those older units, the front diff, locked and the steering wheels would rub hard against the pavement putting a lot of stress on the components. Newer, four wheel drives have two options, either high, or low. Four wheel high, is like AWD, in that all four wheels are turning, but the front Differential performs exactly as the rear one and eliminates the stress'. In four wheel low, it locks the front differential, and both front wheels are applying load. That is where you will have problems unless on loose pavement. But as mentioned, on black ice weather in 2 wheel or 4 wheel drive would not make a difference!

I'm sorry, but this is wrong.

4wd is mechanical linkage between front and rear axles. You are correct that the differential allows for wheels to turn at different speeds, but the problem is that each of the 4 tires travels a different distance while turning. Contact between tires and pavement keeps the differential from being able to do what you are saying.

AWD had a viscous coupling that allows the front axle to too soon at a different rate than the rear axle, preventing the frontline bind.

4 low is differet than 4H, only the gearing is different.

Most if not all AWD full size American trucks just have another differential in the transfer case for allowing speed difference between front and rear drivelines. These AWD transfer cases also have 4x4 mode which locks this center diff. Regular 4x4s have no way to allow for the different speed from front to back so driving on a hard dry surface will bind up the drivetrain.

I think some of the smaller AWD vehicles have a Viscous coupler in the transfer case but I don't know of any full size American truck with it. ;D