4x4 wont stay engaged

[going-strong]

when i put my truck into 4hi or 4lo it dosent matter, it will engage and I can drive down the street in 4wheel. after probably 20 seconds i start hearing all of these grinding noises as my foot is on the trottle. i ease back my foot and put it back in 2hi. I can no put it back in 4 and it does the same thing. A lot of people are telling me it is my actuator or my diaphram. any help would be greatly appreaciated. thanx in advance

[Yetti]

I guess I have ask you to do some diagnosis. the axle is vacuum shifted but its controled by a switch on the T case that shifts the axle fork. I have seen many that were nothing more then a bad vacuum line from the intake. if its a diesel then make sure you have vacuum. all have to have vacuum to the T case "confirm" it then shift it to 4x4 and crawl under it, should have vacuum at the axle(use a gauge) .if your not seeing vacuum from the t case to the axle replace the switch at the T case. easy stuff have fun.

[going-strong]

i have to work all day tomarrow, and wont be able to check out the vacuum till saturday. I will let u know what i find. thanx, by the way it is gas