I actually tested them today to see how far I would slide. My ABS has never worked for the front. Ever. I lock them in the snow all the time, but only in 2 wheel drive. If I am in 4, they will not lock up unless I am standing on them. I think it is because someone messed up the last time my diff was put back together, and did soemthing to the reluctor ring in the diff for the rear ABS.
For you that do not know about real trucks, it is impossable to lock 3 tires, or only 2 on one axle. You can lock one front and one rear at the same time, but not 2 on the same axle unless the other 2 lock as well.
My stopping distances improve 10 fold in 4 wheel drive on snow and wet slick pavement. Never really tried a panic stop in 4 wheel on dry pavement. That would be interesting, assuming I don't puke out my ring gear again.
Funny you asked, first time out in the snow with the new ride. Tested the traction control and 4-wheel ABS brake feature. Pretty happy that when I jammed on the brakes, it worked as they should. I was able to steer while hard on the brakes. Although the brakes did vibrate more so than what I've been used to on pop's GMC Safari AWD ABS brake system.
Some vehicles have 2-wheel disc and 2-wheel drum brakes, ours have 4-wheel disc.
Acceleration on the FWD ride wasn't as fun in the snow though, no crazy twists, turns, 360s, power slides