Weird rubbing noise in 4wd mode?

[truckguy82]

I know this is an old thread, but just incase someone reads it in the next 20 years

 

A 4wd or awd all have what’s boiled down to 3 seperate differentials.

 

Then engine sends power to the center diff, and that sends power to the front and rear differentials. All awd vehicles have some form of this (except electric that have multiple sources of power)

 

the main difference between awd and 4wd, is that when you engage 4wd, you lock the front and rear differential together. They are mechanically attached. This is why there is rubbing when you turn, because the rear tires are moving a different speed than the fronts.

 

in auto4wd mode in our trucks, the center diff is not locked, it uses a series of clutches. When it detects slippage, it start activating the clutchs starting to lock it. This is in essence, an awd system. When you switch it into 4wd hi, it just locks it like every other 4wd truck.

(Our trucks 4wd system is badass)

 

this is why you cant use 4wd on dry pavement, and you can use auto4wd and awd vehicles in the dry