4wheel drive not enguaging.
 

Pull it into 4x4 no light and when I am moving it is making a poping noise. Worked fine 2 weeks ago. What could of happened. Is a vacume line off or is my actuator bad?

It must be something in your vaccum system. If you want to solve this problem permanently get a 4x4 posi-lok. It gets rid of the hole vaccum assembly on the front axle and you use a cable to lock in the axle. Much stronger and better than the vaccum.

make sure the bolts connecting the driveshaft to the t-case are tight!! That was the first clunk I heard...

Mine still does it a little if I try to engage 4wd about 15, but my actuator is worn out and slow.

Its probably your actuator. Try this: Start the truck and engage 4x4. Drive around the yard a bit to make sure things have a chance to lock in. Shut off the engine and pull the t-case back into 4x2, IN THAT ORDER. Get out and try to spin the driveshaft. If it spins freely, your front axle disconnect isn't working, which is usually either a vacuum problem or the disconnect motor is bad.

Next start the truck, put it in 4x2, and drive a short bit. Shut it off and put the t-case in 4x4 IN THAT ORDER. Try the driveshaft again. If it won't turn, the t-case is engaging 4x4 as it should.

Any truck with a disconnect and real 4x4 is going to clunk somewhat when 4x4 is engaged while moving. Having the front axle disconnected and the t-case in 4x2 means that the front driveshaft isn't spinning when the truck is moving (it spins slightly, but only because of the thick fluid and friction). When you shift into 4x4 while moving, the front driveshaft has to catch up to the speed of the rear driveshaft before fully engaging, which is the clunk you hear. Kind of like shifting a transmission without the clutch. Once its engaged all the way, as the linkage finished its travel, the vacuum switch on the t-case is activated and the front axle is connected, which can sometimes cause another slight clunk, but is usually not noticeable.

Jim

I agree

the actuator through wear and tear can get beaten, or rusted out inside where it dont work anymore. Remove it and try to clean it.. If not just posi lock it and forget it..

Tx

I was plowing all day no problem,tried to back up needed 4wd,then a loud clunk and no more 4wd.The actuator pin bent so i maid my own pin out of a bolt and welded a cable to the end of bolt to make my own posi-lok.like it now can use 4lo in 2wd,just like having lock out huds
tom

4x4 swith
 

Had same problems 2 weeks ago. Identical. Checked all vaccum lines, and nothing. Took out the 4x4 switch on top of transfercase, bought a new one for $16 and works great. My old one was sticking, that is why it would work sometimes, and not others. The valve in the switch gets dirt and grease in it and it can't actuate. It sticks.
Jason