2001 Ford F-350 Stuck in 4X4

Forget the age of truck other than rear diff. Every thing else has less 20,000i. Replaced complete locking hub seals rotors caliper all front axle stuff except gears in the pumpkin ok. All this is in good working shape the 4 x4 is locked in once or twice a week on soft or muddy surface while pull goose neck roofing take off to dump site. I get lock manual hubs then get in turn switch on to 4x4 low foot on brake tran. Neutral can't get out 4x4 now I replaced vacume hub lock solenoid still a swing and a mis