i have a 2000 jimmy, put in a 2" pa body lift a few months ago. everything was great. I am an a apprentice at a local ford dealer that decided to send me for some ford electrical training about 450 kms away from home. so on my drive down here i hit the freeway and notice a bit of a hum coming from my rf tire area, however that hum has been there for awhile, and didnt think much of it. so after about 3 hours on the freeway traveling at 120-130kms an hour, i merge off my turn and come to a stop. as i am coasting to the stop, i am hearing a metal on metal screeching sound as i am coasting. apply the brakes and it kinda goes away until i take off again. I had a feeling that possibly the hum noise i am expeirencing is coming from the rf axle locking in and turning the diff? i am staying at a hotel, and they dont exactly want me working on my truck in the parking lot, however i did manage to pull the vacume actuator switch of the tcase, and a little bit of tranny fluid came out. so luckily the autoparts store next to the hotel had one, so i put it in. but really my question is, after i did my body lift, i didnt drill any holes to relocate the 4x4 actuator under the battery tray. i just used the stock holes. i notice there isnt much slack in the cable, and am wondering if its possible that perhaps the cable is pulling the actuator in the axle over becuase the cable doesnt have any slack in it... . ?? i am kinda worried cause i dont have a lot of cash, and i dont want to be stranded on my drive home in a couple days. I did the basic inspection of wheel bearings, and brakes and such, and everything looks good and normal... any other ideas folks?

 

If the noise went away after replacing the vacuum switch, I'd say the switch was leaking vacuum past the O rings inside the switch, (very common problem). When that happens, it can apply partial vacuum to the actuator and cause the axle gear to grind on the clutch gear because it's not fully engaged. Lotta times you can switch back a forth between 2HI and 4HI and the noise will stop. That's a clue that the switch is leaking.

 

so managed to find the highway and go for a rip. the humming is still there.. :S . i am wondering if perhaps that cable from the actuator to front diff doesn't have enough slack in it, and its pulling the cable to engage the axle.. anyone run into this before?