94 Ram 4wd "clanking"

[LandFakers]

My son took his ram out this morning to go blow some snow and we haven't even had to try the 4wd since we've bought it. He described it, and I've heard it to be a clicking or clunking noise while you drive forward after putting it into 4 wheel. could it be in the transfer case or something? The wheel drive isn't engaging so I'm kind of lost.
Some info on the truck is its a 94 ram 2500, reg cab, long bed, 8.0L V10. Thanks guys

[Banksy]

I was going to say u-joints, but the fact it isn't engaging the front axle could be a couple things. 1) transfer case or 2) the vacuum actuator in the front axle that locks in the axle when you shift into 4wd. My bet is is on #2 and you want to hope that's it. Check for broken vacuum line to it.

The u-joints could still be junk though.

[LandFakers]

Originally Posted by Banksy

I was going to say u-joints, but the fact it isn't engaging the front axle could be a couple things. 1) transfer case or 2) the vacuum actuator in the front axle that locks in the axle when you shift into 4wd. My bet is is on #2 and you want to hope that's it. Check for broken vacuum line to it.

The u-joints could still be junk though.

So after I posted I did a little more research, and I found saw people on various websites talking about the vaccuum actuator. I decided to go crawl under the truck and test it out myself. I swapped out the vaccuum lines and no change. Tommorow I will probably drop down the actuator itself and see if the fork inside is moving around, as that is what engages the front axle