Front wheel locked up

While driving, foot on the gas/ not the brake. My 2003 silverado 2500 4x4 6.0 just locked up. While in 2 wheel drive/ manual , not push button 4x4. Got it towed back home, noticed both rear tires rolled. Jacked up the entire front end. Passenger wheel spins freely. removed front driver disc brake, still does not rotate. How do I find out if it's the transfer case, axle, or something else?

Can you rotate the front driveshaft with the wheels off the ground? If not, there may be a differential problem. To eliminate the possibility of the transfer case, match-mark the position of the front driveshaft at the flanges and remove the shaft. If the transfer case drive yoke will rotate, the transfer case is not likely at fault.

The LH half-shaft can also be removed/separated at the drive flange to help isolate the problem, but it might be just as easy to remove the front differential cover and inspect the assembly. At the very least, you can get some fresh gear oil in it. However, if the oil drains out with metal particles in it, things could be more complicated.

https://www.youtube.com/watch?v=zJ1mcAfMfm0

Thanks Blue Bowtie, I've got a more mechanically inclined friend stopping by tomorrow. I'll be sure to mention this.