When put into 4 hi or lo, the light by the selector **** flashes then goes solid that it is locked in, and you can feel it lock in, but, the 4x4 light on the dash that comes on will stay on for 2 seconds then blink off and on, or sometimes go off for quite a while, then come back on. Is this a vacuum problem? The selector is the electric turn ****, not the manual put in.

 

No vacume problem that i know of. Unless I'm missing something there is no vacuum pumps on these trucks and everything is motors. Mine is a manual so no more experience.