ABS brakes on 4x4
 

2010 K-1500. Curious since I live on a steep hill and use 4x4 in the winter and a lot going down hill on the road. Does the ABS system work when it is in 4 wheel drive?

ABS works as designed as long as a part time 4WD vehicle stays in 2WD mode. In 2WD all 4 wheels are able to rotate at different speeds (made possible by the differentials) and more importantly in 2WD both axles are allowed to turn at different speeds because only one drive shaft feeds rpm and torque to one axle. As soon as you shift into part time 4WD (find out which kind of 4WD you have) both drive shafts become connected inside the transfer case and both axles are forced to turn at the same speed. More importantly, when stopping both axles will be slowed down at the same rate (any brake proportioning will be out of force) and the ABS system would get confused. After all, the ABS's job is to detect variations in wheel speeds and act accordingly. ABS will not function properly on part time 4WD systems!
Because part time 4WD and ABS do not mix, most manufacturers offered only rear wheel ABS on these vehicles since the rear axle needs ABS the most, due to the tendency to lock up first.

great info
what about the 3 channel abs systems on the older gens?

I found some info on Wiki about Three Channel

Chrysler, together with the Bendix Corporation, introduced a computerized, three-channel, four-sensor all-wheel ABS called "Sure Brake" for its 1971 Chrysler Imperial. It was available for several years thereafter, functioned as intended, and proved reliable. In 1970, Ford added an anti-lock braking system called "Sure-track" to the rear wheels of Lincoln Continentals as an option; it became standard in 1971. In 1971, GM introduced the "Trackmaster" rear-wheel only ABS as an option on their rear wheel drive Cadillac models and the Oldsmobile Tornado. In the same year, Nissan offered an EAL (Electro Anti-lock System) as an option on the Nissan Presedent, which became Japan's first electronic ABS

ABS brakes on 4x4
 

Not sure what "part time 4x4" is. I am assuming you are talking about cars with all wheel or the truck when it is in "auto". I think you answered my question that the front brakes are not in ABS function when I have the truck locked in 4 wheel drive.
Thanks for the information.

4wd systems are part time which means they are not meant to be run on drive pavement. running on dry pavement stresses the tcase.


AWD systems can be run on dry pavement due to a viscous coupling which connects the front and rear driveshafts.


i'm not a fan of the auto setting. for me, if its slippery it goes into full 4wd and if its dry 2wd.

Until this question was posed, I never even considered what the abs system was doing in 4wd. I tested my 2000 sierra 3 channel system as I could not find and gm service info specific for my model. the abs did function in 4 hi and 2wd.