Auto 4wd noise?

pancepance · February 7, 2015

Wondering if someone can confirm of deny something for me please.
When using the "auto 4wd" position of the selector if there any noticeable rotational noise difference?

I am noticing that when in the auto position there is a noticeable noise happening. I would expect some noise change in the full 4wd position but in my Yukon when auto 4wd is selected there is no noticeable sound difference. I am well aware of how a 4wd system works and when to use and not use it. During the recent snows I was using the auto and realized that when its selected it sounds as though the transfer case is engaged and has a gear-gear noise. I haven't heard this on any of my other GM's with the auto option.
Before I go tot the dealer I figured I would see if everyone has a noticeable noise whenever using the auto mode?
Truck is a '14 gmc sierra.

Thanks

Spurshot · February 7, 2015

Essentially no noticeable noise in my 2014 or any prior models I've had. Try 4 hi as we'll. shouldn't be any there either.

Brian S. · February 7, 2015

I didn't notice the noise, but with my 2014 Silverado 4.3l I noticed some vibration on acceleration between about 20-40 mph in Auto.

Now with my 2015 Sierra 5.3l I don't have the vibration.

With both of them I could tell when disengaging the Auto, felt like a little strain was relieved on the engine. I don't remember that with my 2002, 2006, or 2010 5.3s, but I am getting older.

redwngr · February 7, 2015

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Edited February 7, 2015 by redwngr

timstruck · February 7, 2015

I have experienced this as well with the recent snow. I can say that I heard and felt the noise/vibration in both 4a uto and 4 hi. I too am familiar with 4 wheel drive vehicles, and I can say that this is very similar to a 2000 ram 4x4 I had. once engaged you could feel the gears. I don't know the exact vocabulary, so forumsters, please don't roast me, but obviously the ram had a different 4 wheel drive set up with the solid front axle, etc.

I will also add that the vibration didn't sound harmful... you could just tell something else was engaged on the drive train.

Silverado-Hareek · February 7, 2015

I have no noise with my 4 auto mechanically speaking. (I do have the high pitched electrical squeal discussed in another thread that has to do with the 4 wheel drive knob/circuitry). I have not used 4hi or 4 lo yet. I do remember on my 2007, 4auto was silent but 4hi had a sound as if something new was engaged mechanically (the front drive shaft obviously) but it wasn't a bad noise like a grinding or anything like that, just the noise of something else working. I expect to hear something similar in my 2014 when I use 4hi but so far, 4auto is silent....like I'm driving in 2hi.

Green 1364 · February 7, 2015

I have this as well, actually sounds like 4WD is engaged in auto on dry roads. Wondering if it is?

BigBadSierra · February 7, 2015

In auto the front transfer case is still engaged. The computer reduces and increases the torque to the wheels as needed.

This is why the fuel millage drops some in auto. At the minimum the transfer case is spinning.

I can tell by how my truck sounds if the auto is on vs the sound it makes in 2 hi.

pancepance · February 8, 2015

I am fairly familiar with 4x4 trucks having owned them for many years. This one has got me wondering though. Especially after I compared it to my '12 Yukon with a similar 2wd, auto, 4hi, 4lo selector.
Theres no noticeable difference between the 2wd and auto in the Yukon. on the same roads in same conditions.
The Sierra absolutely has a noticeable mechanical constant noise. I realize the transfer case would be engaged in some form or the hubs would be locked but in a situation where there would be no need for power to be applied to the front gears I would expect not to hear it as though it were in 4hi. When switched to 4hi it makes the same noise. I would expect a change in noise if using 4hi but the auto has me wondering.

It almost as though the "auto" part of it is not working and its just in 4hi. Something is definitely turning constantly and making noticeable sound when doing so. It doesn't go away from auto to 4hi. Only gone in 2wd.

Time to visit the dealer and play the "its supposed to sound that way" game. I looked on the lot today and see a very similar '14 for sale so at least I can have them demonstrate how it will happen in that truck I suppose.
Just seemed odd to be making that much noise even for 4hi.
Will update on findings as they progress.

Thanks for the comments

GMTEC2 · February 8, 2015

I also have the noise as described. It's definitely a noticeable change from 2 to Auto and 4 hi

2014 GMC Sierra

seansharley · February 8, 2015

Mine has it

Yamiryder · February 8, 2015

Mine makes noise from the switch. It's a very high pitched noise when in AUTO or when engaging 4 hi. I took it to the dealer, they did a recall. Seemed to make it slightly better but the noise is still there. I've contacted GM as well. Seems that there isn't anything they can do about it. Pretty lame if you ask me. I shouldn't hear noise from my switch.

Isriam · February 8, 2015

Mine makes noise from the switch. It's a very high pitched noise when in AUTO or when engaging 4 hi. I took it to the dealer, they did a recall. Seemed to make it slightly better but the noise is still there. I've contacted GM as well. Seems that there isn't anything they can do about it. Pretty lame if you ask me. I shouldn't hear noise from my switch.

hes not talking about the high pitched squeel from the switch. thats another issue. this is about transfer case noise. auto isnt really auto, its more like 4wd and why i refuse to use it.

tbarn · February 8, 2015

My '14 had it. My '15 has it.

pancepance · February 9, 2015

Yes, I get a noise during the switch from one position to another. My concern is a constant mechanical gear/gear type noise. Similar to a rear end as its starting to go. This noise will increase/decrease with speed and is only apparent out of 2wd.

I rode in a '14 Silverado today that had no noticeable noise when operating in auto or 4hi. Compared to mine its a night and day difference.
I also noticed today that when in auto if I come to a complete stop and reverse there is a clunk as a start in the other direction. Then if I stop and go the opposite direction it clunks again. Similar to the sound a bad U-joint can make when starting from a standstill. This is new and I hadn't noticed prior but it does it consistently each time. Just one time from standing start at regular pace. Not any type of power takeoff, just as if you were making a 3-point turn in a parking lot. Each time I change direction there's a clunk and then not again till I've come to a complete stop and restart motion.