Hey guys...

I've had this truck since July, and have had it in and out of 4WD 5-6 times, all at very slow speeds (under 10 mph); never noticed any issues. Tonight, I found myself on snow/ice out on the interstate, so I tossed her into 4WD High. I let off the gas and pressed the button... and she went into 4WD quickly. I was running around 50 mph at the time.

When I went back on the throttle, I immediately noticed a low-level noise - sounded like (and felt like) I was running on the small rumble strips on the shoulder of the road. Mind you, it was not that loud; but it was noticeable. When I let off the gas, the noise dropped, but you could still feel it a bit. Back on the gas and you could hear it/feel it again.:shake:

I took it back out of 4WD; the noise didn't go away until I let off the gas, Once I did, the noise and vibrations went completely away.

I repeated this 2-3 times, and it seems there's a vibration/noise anytime I was in 4WD. Anything below 40 mph it wasn't very noticeable. 50-60 mph and it's noticeable.

This truck has never been abused, and has been well maintained. I find it difficult to imagine that I have something wrong with my 4WD. Any ideas what might be going on?

:help:

mine seems to do the same thing...I read somewhere (here) that this is normal,but it almost sounds like something is loose or starting to go out

X3 mine did it this weekend at the exact same speed. im running it through the shop today to the techs can find anything.

I have owned and driven a LOT of 4x4's over the years. What you describe sounds normal. You have to consider that you are turning a whole lot of drive gear when you are in 4x4, and even when you are on snow the phenomenon of driveline wind-up is still occurring, it's just not a problem because the tires can slip. There is a lot going on when you are driving all 4 wheels.

first I wouldnt shift into 4x4 at 50 mph. vibration like a rumble strip, that has got to be universals.

good luck
drive safe

first I wouldnt shift into 4x4 at 50 mph. vibration like a rumble strip, that has got to be universals.

Fair enough. I know that you're not expected to stop to shift from 2WD to 4WD... so what is the max speed you should be going to shift from 2WD to 4WD?

BTW, the owner's manual says nothing about this subject.

2HI to 4HI or 4H to 2HI can be shifted at any speed, any HI to 4LO must be done going 2-3 MPH.

Noticed the "rumble strip" noise on mine this morning while in 4wd too. Have driven 4wd's for years and have heard the normal "extra parts" moving noise but never this. Will have to do some more driving to get use to it I guess if it is normal! :eek:

2HI to 4HI or 4H to 2HI can be shifted at any speed, any HI to 4LO must be done going 2-3 MPH.

Yup the manual says 'any speed' for 2hi -> 4hi -> 2hi

Yea I was coming thru Lexington Ky earlier this week at night and had to hit mine at about 50 (which I hate doing...makes me nervous) due to all the ice and pileups from ignorant drivers. Its completely normal on these trucks to hear some sort of noise or feel it pull one way or the other when 4wd is engaged. Thats why I only use it when completely neccesary. Nothing like sitting on freeway for 2.5 hours due to it shut down.

Also mine always locks the rearend so when I make a turn it skips... it actually feels like the whole damn frontend is binding and about to break. Had wife get out and check few years back and it was from rear being "locked".

Yeah - in the space of about 3 miles, there were 9 accidents on the north end of Lexington. You must have passed us... or we passed you. It's a small world...

:D

I too am having this same issue. It just amazes me to find this thread. I was just curious to see if anyone else was having this same sound when using 4HI and this was the 4th thread in the drivetrain section! Anyway, last weekend up at Lake Tahoe I needed to use 4HI on pavement. But I never went above about 35-40 MPH when in 4HI. I only noticed the noise whenever I was accelerating. When I released the throttle the noise disappeared. I would be interested in what MPRICEDURAMAX found out from his trek to the stealership.

X3 mine did it this weekend at the exact same speed. im running it through the shop today to the techs can find anything.

Make me # 100. My 05 aswell as our 03 Duramax makes that humming type of sound when in 4hi. My 2000 cc gas job never made any such noice though. Kind of weird, But as common as it sounds to be, I am assuming all is well!!;)

Yeah - in the space of about 3 miles, there were 9 accidents on the north end of Lexington. You must have passed us... or we passed you. It's a small world...

:D

Yes sir! Love how all those idiots just kept going when they see its wet pavement with a glare and temp is 14*. Amazing isnt it?

As far as 4wd thing....these trucks 4wd are super strong from what I have seen and they are not intended on for using on drive payment. I think the noises you are hearing is just the normal sound of all the extra gears and chains turning under the load of the engaged drivelines. Mine pulls hard when you mash the gas (in the snow) and to me thats just saying its there and working. I have seen 1000hp diesels start from the line in stock 4wd front ends soooooo......

I also get this noise but not a constant noise. I wasn't sure if this occured before the lift or not. A guy i work with is an ex GM mechanic was saying chevs have always made this noise. I had an f150 that never sounded like this. Anyone still get this noise after a front drive shaft change out?

The failure to stop the 'rumble' when you took it out of 4 wheel drive until you let off of it was due to what is called Torque Lock. The splines are under load and can't slide apart until the load on them is released. Learned about it from a Jeep engineer when I asked about the reason my Grand Cherokee wouldn't stop wheel hopping in turns after using 4 wheel drive.

OK - I figured that was what was happening, just didn't realize it had a name. Torque lock makes sense. However, I was real surprised to find that there was that much driveline wrap. Guess it makes sense, but I would have thought that my Avalanche would have exhibited similar behavior... but it didn't.

:think:

As I've indicated in several of these threads out here, my last truck was an '02 Avalanche, and I had that thing in and out of 4WD and Auto/4WD at various speeds and under various conditions. I've never experienced anything like this 2500 HD. But... if it's normal, then I'll treat it as normal and just watch it as I drive.

:driver:

I always do what I had to due with my old 79 truck.... When taking outta 4wd I back up a little to make sure all loading is out of the drivetrain.

OK - I figured that was what was happening, just didn't realize it had a name. Torque lock makes sense. However, I was real surprised to find that there was that much driveline wrap. Guess it makes sense, but I would have thought that my Avalanche would have exhibited similar behavior... but it didn't.

:think:

As I've indicated in several of these threads out here, my last truck was an '02 Avalanche, and I had that thing in and out of 4WD and Auto/4WD at various speeds and under various conditions. I've never experienced anything like this 2500 HD. But... if it's normal, then I'll treat it as normal and just watch it as I drive.

:driver:
I believe the Avalanche has Auto Trac which incorperates some kind of clutch system to let the diffs spin at slightly different speeds. I'm sure someone here can confirm this. Binding in the drivetrain of our trucks will make some strange noises. I had a vibration problem in 4hi after installing a 6" lift kit. A CV front driveshaft cured that, but I still get that low frequency humming when driving on dry pavement in 4hi. Has anyone broken anything yet from this?

well when my transfer case finally got a hole rubed in it i had vibration like you say for a while then it started making popping noise every so often my truck never made any noise or vibe untill there was no fluid in the transfer case might wanna check it out when i got were i was going drained it out there was only a cup of the most black oil youve ever seen flushed it out and filled it back up put a small stainless screw in the whole and some metal filler paste works fine now exept every once in awile it still does that popping thing when i get on but its still working and its been like this for awile now im in Ak. so its 4wd almost all winter

anybody got any clue what that popping noise is

I believe the Avalanche has Auto Trac which incorperates some kind of clutch system to let the diffs spin at slightly different speeds. I'm sure someone here can confirm this. Binding in the drivetrain of our trucks will make some strange noises. I had a vibration problem in 4hi after installing a 6" lift kit. A CV front driveshaft cured that, but I still get that low frequency humming when driving on dry pavement in 4hi. Has anyone broken anything yet from this?

can shift my LMM from 2L to 4L at 70mph no problem.

haven't heard any noises, either... at any speed.

LMM uses AUTO-TRAK II Fluid in the transfer case, 75w-90 in the diffs.

as to the LLY series, not sure

you can shift at any speed

well when my transfer case finally got a hole rubed in it i had vibration like you say for a while then it started making popping noise every so often my truck never made any noise or vibe untill there was no fluid in the transfer case might wanna check it out when i got were i was going drained it out there was only a cup of the most black oil youve ever seen flushed it out and filled it back up put a small stainless screw in the whole and some metal filler paste works fine now exept every once in awile it still does that popping thing when i get on but its still working and its been like this for awile now im in Ak. so its 4wd almost all winter

anybody got any clue what that popping noise is

My brain, trying to fill in all of your missing punctuation. Dude... periods, commas, and semicolins are your friend!

;)

Thanks for the suggestion. I'll check the fluid level this week.

When my transfer case finally got a hole rubed in it,I had a vibration like you are saying, for a while. Then it started making a popping noise every so often. My truck never made any noise or vibe untill there wasn't any fluid in the transfer case. You guys might wanna check yours out. When i got were i was going,I drained it out, there was only a cup of the most black oil you've ever seen left in there. Any way I flushed it out and filled it back up. I put a small stainless screw in the whole with some metal filler paste around it. Works fine now exept every once in awile it still does that popping thing, when i get on it. Its still working and its been like this for awile now,im in Ak. so its in 4wd almost all winter.

Anybody got any clue what that popping noise is?

By the way I dont think you need commas periods ect. to crawl under your truck and make sure you still have fluid in your tc. If u dont it could be a :badidea: BTW:Nothing_f

My brain, trying to fill in all of your missing punctuation. Dude... periods, commas, and semicolins are your friend!

;)

Thanks for the suggestion. I'll check the fluid level this week.

:funnypost):h