I had the sasme thing happen to me on the way home from work one, except I was only able to accelerate upto thirty mph. It' still under warranty so I took it the dealer i bought it from. They wouldn't even look at the alternator untill i bought new batteries as they were shot. Had the truck only three weeks when this happened so I complained to sales manager that they should spring for batteries and they did. After they got the new batteries they tested the alternator and low and behold it was dead. This was after about a week arguing with them that it was indeed my alt. and not batteries. Ended up costing $50 for the alt. instead of $200 for new batteries and alt.
1999 K3500 Crew Cab 6.5L TD