2005 GMC 4x4. I'm hearing grwoling noises similar to when you engage the 4wd on dry pavement. I suspect 4wd switch is malfunctioning but not sure what exactly is causing this sound. It sounds like I have engaged the 4wd but the button/switch is in 2wd. I'm not sure that this is what is happening and I'd appreciate any suggestions to tell the dealer/service department. By the way, they say they can't hear it which is total BS and they say they have "checked it out" (tests?) and everything seems to be fine .
It doesn't do it all the time (I hate that) and it lasts for different periods of time, some times it is louder than other times.  The buttons/switches on the dash are as follows from top to bottom - 4Auto, 2wd, 4wd, 4low.  I can switch from 2wd to 4auto or 4wd and then back to 2wd and the sound goes away. The sound may come back in a couple of seconds or not come back at all until the next time I drive it.  It isn't really loud but I can hear it and feel it in the pedals and the steering wheel.
Is there a sensor or switch that engages the 4wd that could be going bad? This thing is really annoying after a few miles.
Any suggestions are greatly appreciated!
Oh yeah, I have two sets of wheels/tires and it does the same thing on both sets. Right now the original factory tires/wheels are on it and they are an all season tire. The others are wider performance style tires/wheels.
Thanks on advance.
(this web site is great!).
 

You souldnt be getting any "growling" noises coming from your truck even when you put it into 4 on dry pavement.  If you can feel as well as hear the noise then it tells you that its not the switch but most likely the driveline components that are not working correctly.  The switch is probably continually compensating for a mechanical problem within the 4WD engagement syst. within the front axle or transfer case.  If it happens while the truck is operating normally in 2WD, and you can feal it in the pedals and steering wheel i would suspect the Tcase.

I do remember an instance when I engaged the 4auto because I was spinning the rears in some large gravel and depp/wet snow. I let off of the pedal and put in in 4auto and a couple of seconds later I gave it a little gas and there was a pretty loud kerplunk. It engaged the 4auto and it came out. I'm not sure if this is when I started hearing the noise though.

Also, I was driving down the road and ran into some slick spots and slick bridges. I put it in 4auto and the light on the 4auto button just flashed for about 20 or so seconds, and then another big kerplunk and it engaged.

Thanks for your help MUDNUTT. I'll relay the info to the dealer. Hopefully I can get something done about it (and buy him a hearing aid!).

that is undoubtably a mechanical error in either the vacuum actuated front axle assembly or t-case. try puting the tranny in N, then push 4Lo and see if it engages correctly without rolling the truck. if you have low gear no prob, then the axle is prob ok and the T case is not engaging 4hi. If no dice with 4 Lo either then probably the axle not engaging. If it is an axle prob you would never know driving in 2wd.

his truck is new enough it dont have the old vacuum billow pump like the older trucks had.  these trucks have a heated actulator style engagement on it that i forgot how it works(my uncle explained it to me awhile ago) but sometimes the same thing happens in my dad's truck he has a 2001 chevy halfton 4x4  and sometimes on the ice if you just throw it into auto 4x4 or 4x4 you can hear sumthing grinding/growling comming from the front floorboards (front differential trying to engage) all i do is just hit the brakes and give it a second to engage and the big bang you hear is it catching a gear very hard.  also when im in 4x4 with that truck and sumtimes i turn on a harder surface i feel a bit of pressure on the steering wheel and almost a growling noise (i think this is just the steering pump pushing fluid through the rack n pinion) but on your truck should be equipt with the message center (ours sometimes has the service 4x4 message in it when we use the 4x4 but we havent had it checked out yet) and the same message appears probably take it to another mechanic to have it checked out.  something really easy to check would be if you get a chance get a drain pan and drain the oil in the front differential(if equipt with a skidplate you have 2 remove it) and if the oil has any metal shavings in it i would have it checked out and if you see alot of shavings i would have it replaced. make sure you put in some of the same type of oil recomended by gm

I had a 99 chevy blazer that started making weird growling noises, and vibrations at odd times.  Sometimes it would happen when engaging the 4wd system, and other times it would occure under hard braking.  I chased the problem around and whent to a few different shops before I finally found that I had a bad C.V. joint in the front end.  I am not sure how to check a C.V. joint other than to look and see if the boot is torn.  In my case it was not.  The joint was just bad.

Good luck.

That's good info for this rookie. Thanks Needformud and guppyfish!
I hope I can get the service manager to admit that there is a noise. It isnt very loud, sometimes you can barely hear it. Now today on the way home from work it was definitely something you can hear. The next time I'm driving it and I hear it I think I'll just drive it to the dealership and tell him to go with me before it stops.

Edited 2/21/2006 5:25 pm ET by wtfletch

the side bearings in your front diff could be failing. pull the drain plug

and inspect for metal debris. the bearing preload was setup to tight

from the factory on the side bearings. this could be your problem.

p.s save the fluid and debris if this is your problem. show them to the service advisor

Thanks, I'll check the fluid out and see if there is any metal in there.