Auto 4wd noise?

Liquorice · February 9, 2015

I have a 2014 SLE Sierra.

I have no noticeable noise difference between 2H / Auto / 4H

I live in Canada so I've been using Auto and 4H quite a lot in the last few months.

I can tell when it's in 4H but only because there is some resistance in the steering if I do tight turns.

Other than that, it's almost impossible to tell unless you look at the switch.

(I don't think I've ever used 4L, and probably didn't with my last truck either)

Sam :-)

nards444 · February 9, 2015

Every truck ive owned including my 14 has some noticeable pitch in the 4wd drive system.

Spurshot · February 9, 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.

I believe "Auto" is an open differential in the transfer case (front to rear). At least that was the case in past models. "4WD" is a locked output front to rear.

nards444 · February 9, 2015

I believe "Auto" is an open differential in the transfer case (front to rear). At least that was the case in past models. "4WD" is a locked output front to rear.

The common falicy that many beleive is auto just kicks in 4x4 when it needs it. In auto the system is engaged, its just lacking power. So when in auto you can and will see an mpg decrease.

BigBadSierra · February 9, 2015

The common falicy that many beleive is auto just kicks in 4x4 when it needs it. In auto the system is engaged, its just lacking power. So when in auto you can and will see an mpg decrease.

It increases and decreases the torque to the front wheels as needed. In my mind it's more like wheel assist!!!

It's backwards to most AWD vehicles as they are really front wheel drives with rear wheel assist. Most AWD can't push themselves up a hill if the front wheels have zero traction.

There are exceptions some Isuzu and Mitsubishi and a few others have incredible AWD systems. However they cost much more.

I've already discover 4x4 with a full lock is needed to get up steep inclines as the Auto just can’t get enough power to the front wheels.

In 4 low I can drag myself out with just one wheel catching.

jsnooks · February 16, 2015

My 2014 got the same noise in 4a and 4hi.. When I switch t back to 2 wheel drive it goes away? It seems like the sound is more noticeable when I press on the gas pedal to pick up speed in 4a and 4hi..

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Super 8 · February 16, 2015

Put 1000 miles on a 14 last week towing 4000 lbs. Sound was very noticeable when switched to auto, since I unhooked the trailer it doesn't make the noise anymore?

Edited February 16, 2015 by Super 8

Dmcortez · March 23, 2015

I recently purchased a 2015 GMC Sierra SLT. I had a 4 inch pro-comp lift and 33's Toyo M/t's installed by a gm authorized shop before I picked up the truck from there dealer. Within 200 miles I noticed the same symptoms described here... When in auto mode ( the roads had snow and ice on them) I noiced a growling and a weird feel... Like driving on rumble strips. When I took the truck into the dealership they said when they opened up the transfer case there were metal shavings in there... They said the chain had a lot of play in it so they replaced the chain and bearings ... Put it back together and it's doing the same thing. Now they're starting to lean towards the " it might be the lift causing it" card. Can anybody here confirm if they're having the same symptoms on a stock truck ( no lift)? I would love to call BS on the dealership. The truck is still at the dealership and I just want them to install a new transfer case... Truck has been in the shop longer than its been in my garage. Not happy

Isriam · March 23, 2015

I keep telling people to stop using Auto and either use 2WD or 4WD but I guess it takes a few transfer case issues before people realize that Auto is a crappy AWD.

irish4life8911 · March 23, 2015

I keep telling people to stop using Auto and either use 2WD or 4WD but I guess it takes a few transfer case issues before people realize that Auto is a crappy AWD.

When My truck was in auto 4wd, my truck was always in 4hi. Someone called me stupid I this forum for saying that. But my truck was in 4wd while in Auto. There w was no 2wd while in Auto.

I'm thinking that people don't realize that while in Auto 4wd, their transfer case is leaving 4hi engaged and they are traveling faster than you should while in 4hi, thus doing damage.

Im fine leaving it I 2wd and switching to 4hi when needed.

But plan on mentioning it when I go I for service

Jon A · March 23, 2015

I keep telling people to stop using Auto and either use 2WD or 4WD but I guess it takes a few transfer case issues before people realize that Auto is a crappy AWD.

Yeah, using Auto 4WD for 200 miles on icy roads ruined his transfer case. Get real.

Can anybody here confirm if they're having the same symptoms on a stock truck ( no lift)? I would love to call BS on the dealership.

No, there was something screwed up with that transfer case. A 4" lift should have no effect.

There w was no 2wd while in Auto.

There should have been. Unless you're spinning the rear tires there should only be a very small amount of torque going to the front wheels, depending upon speed, and plenty of slippage is allowed between the front and rear to prevent binding even on dry pavement. The most common causes for it seeming to always being locked in 4WD while in auto are a bad wheel speed sensor or a mismatched tire diameter (mix of old and new tires, different brands, different air pressures, etc).

txchevy4ever · March 23, 2015

Auto 4WD is not the same as 4HI

The statements below indicates that it behaves significantly differently than 4HI.

AUTO (Automatic Four-Wheel Drive): This setting is ideal for use when road surface traction conditions are variable. Do not use AUTO mode to park on a steep grade with poor traction such as ice, snow, mud or gravel. In AUTO mode only the rear wheels will hold the vehicle from sliding when parked. If parking on a steep grade, use 4HI to keep all four wheels engaged.

AUTO (Automatic Four-Wheel Drive): Use when road surface traction conditions are variable. When driving in AUTO, the front axle is engaged, and the vehicle's power is sent to the front and rear wheels automatically based on driving conditions. This setting provides slightly lower fuel economy than 2HI.

Ridersfan · March 23, 2015

Transfer case & front driveshaft are full timing it in auto 4wd, the front axle engages and disengages when required... that's the auto part. It is normal to hear some noise difference between 2hi and auto 4wd. 4hi will also have your front axle engaged too so you get even more noise and the jump around turns on dry pavement... all by design, I don't think you have a problem

txchevy4ever · March 23, 2015

Transfer case & front driveshaft are full timing it in auto 4wd, the front axle engages and disengages when required... that's the auto part. It is normal to hear some noise difference between 2hi and auto 4wd. 4hi will also have your front axle engaged too so you get even more noise and the jump around turns on dry pavement... all by design, I don't think you have a problem

Yep, that's 100% correct. Having had 3 Chevy's over the past 15 years with Auto, this behavior is consistent.

Isriam · March 23, 2015

Here we go again Jon. i've replaced 3 transfer cases due to vehicles being driven in Auto. I can prove that driving these things in Auto 24/7 is bad for them.