Trans won't come out of 4WD properly

I have a 98 F-150 Extended Cab, Triton V-8, 5.4 Litre engine. Approx. 114 K miles....

My problem is that the few times I have used 4WD, It would'nt ome out. After I drove it back and forth, (rocked it) drove it down the road,
Undone the battery cable, Let it sit over night, Came back, hooked up the battery,Turn the switch back to 2WD, And it came out of 4WD....

Any suggestions of fixing this problem, So far, Modmech's help, I am batting 2 for 2

Appreciate any help

It sounds like a computer problem to me. When you disconnect your battery cables, it resets your computer. You ought to go and get a diagnostic test ran on your truck and find the trouble codes. The electronic 4wd on the truck may be shorting out. Check fuses also.

Hope it helps!!!