I HAVE A 2001 250SD THAT LOCKS UP WHEN I TURN THE WHEELS.I'VE CHECKED EVERYTHING. ANY IDEAS?  

Can you explain your problem a little bit better?  

IFIF I LOCK INTO 4WHEEL AND TURN THE WHEEL THE TRUCK STOPS ROLLING. IT SOUNDS LIKE A BAD BEARING,AND IF I EASE ON THE GAS IT TRIES TO SPIN THE TIRE.I HAVE A DANA 70 LOCKER AND NOW THINK ITS NOT SLIPPING WHEN I TURN-I PULLED THE COVER AND IT LOOKS LIKE THE SIDE GEARS&PINION GEARS ARE CHAFT SO I DON'T IF THAT WILL DOIT OR NOT? WHAT DO YOU THINK?   

if you have a locker in this truck and it is in 4wd then the truck is doing exactly what it is supposed to be doing. that tire spin is because the wheels are locked by the locker and they are trying to turn at the same rate.  by the way you describe it im sure you are doing this on dry pavement.

if you put it back in 2wd it should turn much easier. 4wd is not made for dry pavement driving and it acts on the the assumption that one or more tires will be able to slip on the terrain its made for. therefore avoiding all that driveline lockup you get on the pavement.

if the truck still almost stopping itself in 2wd then you have a problem.

it locks up on gravel,dirt,grass,ect.makes a grinding pop sound and when i shift back to 2 wheel it stays locked untill i straighten the wheel.