i have a 01 supercrew 4x4 and the 4x4 wont pull. the transfercase and front diff both lock in but the front tires will not pull. wut could this be?

 

Check your vacume operated hubs...

 

There are no "vacuum operated hubs."

All the mechanical disconnects are in the front differential. When you say that the front diff "locks in", do you mean that the linkage moves over? If it is moving then it's not a vacuum problem, it is the shift fork inside the differential. I had to have mine replaced a month ago and my truck only has 33,000 miles on it. Was a $450 job, but I could have done it myself if I would've researched first.