4 Wheel Drive/SUVs: 4x4 blinking lights

Question
on my 99 explorer the 4x4 lights are blinking 6 times then stop ,it does engage when switched but at speed in 4x4 auto it makes a roaring noise it increases and decreases with speed what could it ,i've been told speed sensors or shift motor or vaccum lines how do i find out or what do you think

Answer
Jeffrey,

It's possible that the problems are speed sensors, or shift motor, vacuum, etc., but the roaring noise sounds more like a mechanical, or gear problem in the transfer case.

I would take it to a reputable transmission shop that is familiar with 4x4s, and have them check it out, before it freezes up, or breaks a case.

Without, actually listening to it, it's really hard to evaluate the actual problem.

Carl