4wd actuator problem

I have a 2000 Jimmy with 33000 miles on it. I just had a problem with a loud whining and vibration from the front passenger side underside. I put it in 4wd and the noise stopped. Back in 2wd and it started again. Had it towed to my dealer and they diagnosed it as a sticking 4wd actuator and replaced the switch. Seems fine now but I don't understand what went on. Hardly ever use 4wd and have not used it for about a month so Its only been in 2wdr. Does not make sense to me why the noise would just start with no movement out of 2wdr and then stop when I put it in 4wd if the switch was faulty. The dealer's counter person did not know the answer. I just want to be sure that the switch was the only problem. Thanks for any imput.

there is a vacum operated switch on the transfer case to allow vacum to flow to the front axle diaphram that engauges the front axle most likely the switch developed an internal leak causing the diaphram to partially engauge the front axle causing the actuator fork to grind on the front differential ring gear

Thanks Intimida. If it makes sense I'll consider the problem fixed and not worry about it.

My 01 Jimmy makes that same type of noise when I decelerate, usually when I take my foot off the gas and before I apply the brakes, from speeds over 60. When I switch into 4 WD it stops but when I switch back to 2 WD it begins again.

I just posted my problem today, 6/21. Thanks.

Do you happen to have a part number for that switch? Thanks again.

I have a 2000 Jimmy with 33000 miles on it. I just had a problem with a loud whining and vibration from the front passenger side underside. I put it in 4wd and the noise stopped. Back in 2wd and it started again. Had it towed to my dealer and they diagnosed it as a sticking 4wd actuator and replaced the switch. Seems fine now but I don't understand what went on. Hardly ever use 4wd and have not used it for about a month so Its only been in 2wdr. Does not make sense to me why the noise would just start with no movement out of 2wdr and then stop when I put it in 4wd if the switch was faulty. The dealer's counter person did not know the answer. I just want to be sure that the switch was the only problem. Thanks for any imput.

I just had that switch replaced on my 2001 SLE and it seems to have done the trick for less than $70 at the dealer. Thanks for the great info.

I just had that switch replaced on my 2001 SLE and it seems to have done the trick for less than $70 at the dealer. Thanks for the great info.

Had the same loud noise in 2WD coming from the front right side of my 2000 SLE. Replaced the transfer case vacuum switch for $80. Problem fixed! Thanks for your help!

Had the same loud noise in 2WD coming from the front right side of my 2000 SLE. Replaced the transfer case vacuum switch for $80. Problem fixed! Thanks for your help!

That switch is 15 bux at most autoparts place. Only tool needed to replace it is a 7/8 box wrench...:(