It shifts in out of 4wd fine. I thought its odd the universal joint wore out on the front drive shaft.We hardly ever use the 4wd.The front drive shaft turns with the rear drive shaft all the time but the front tires engage after pushing the button.is this right or do i have a problem?
Dose the front drive shaft always turn while in 2wd? on 1999 Chevrolet Silverado 1500
That is Wrong. Your 99 has an axle disconnect on the passenger side of the front axle assembly. When disconnected properly, the front right wheel is disconnected from the driveline. Your front left wheel simply spins the driver side "Side Gear" and the "spider gears". Because the differential is open, the ring gear does not rotate, thus the pinion gear does not rotate, thus the driveshaft does not rotate in a normally functioning 4x4 Silverado.
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You are correct and there is no problem with the 4wd system on your 1999 Chevrolet Silverado 1500. The front drive shaft is always turning and the front differential locks to engage the 4WD. Please see the following Pepairpal article for more information - http://repairpal.com/gm-4wd-warning-light-issues.