I have a 1989 F-150 with 149000 miles. It's a great truck but the 4 wheel drive only works part of the time. The 4 x4 lights come on but the 4 wheel drive doesn't activate. Then the next time I try it the 4 x 4 light comes on and it engages. There isn't anything I do to make it work. It just works. Does anyone have a problem like this?? Thanks for the help