today, I put the truck into hi 4WD and the indicator light on the dash that shows "4WD" flickered and then went out. Is this just the indicator light or is something wrong with the actual 4WD. I tried to see if the truck was going in 4 wd but I couldn't tell. Any helpful suggestions? how do I know that the 4WD is working?

 

You know by if the front axle is driving or not! LOL

It's possible the bulb burned out - it IS 12 yrs old now!

Otherwise, most likely cause is a vacuum leak in the ADD system so the collar didn't slide over far enough to truly latch. Do a search on "ADD vacuum"

 

One way is if it has manual locking hubs is to put it in 4 hi and lock 1 hub climb under and turn unlocked axle if you cant turn axle should be working.If not put in 4 hi or lo and cut wheels deep it should feel like its in a bind when cut deep if working or put in 4 hi or lo and try to turn front drive shaft it shouldn't move but 1/4 turn at most. Maybe this will help.

 

thank you all