First time using auto 4wd extensively. Horrible MPG

[bloggs]

2014 Silverado 1500 LTZ with the 5.3 and automatic electric transfer case. I have about 6800 miles on it, and I have used the 4wd when towing and pulling, but typically just leave it in 2wd for any normal driving. I am typically getting around 16-17mpg in 2wd, but due to the snow around here I switched it into Auto a few days ago. After driving around for a day or two, I noticed a couple things.

 

My mileage is absolutely awful. I am getting 4-8 mpg most of the time now, and there is a fairly heavy "dragging" feeling when running anywhere under 25 or so mph. At about 25, things seem to loosen up a bit and my mileage gets a little closer to 10-12. The engine also seems to stay in v8 mode at all times below 25. I've switched into 4 high a few times as well, and the ride feeling and mileage seems identical to auto, so my guess is that it may be staying in 4wd pretty constantly up until I get to higher speeds when in auto. It does the same thing whether on snow/ice or dry pavement. I've probably put a hundred miles in auto now with no noticeable improvement.

 

I have owned 3 of these 1500s now over the past decade, and have not had any noticeable break-in period on the 4wd on any of them, in fact, I don't believe either of them had any significant difference in handling or mileage when switching to auto at all.

 

One other thing that may be playing in here, about when it first got really cold, my proximity sensors on the front of the truck started getting a bit excitable. At low speeds they have occasionally been indicating that I am right on top of something on the front left corner.

 

I am going to try taking it to a dealer as soon as I can get it in, but based on my previous experiences I don't expect them to find anything unless I can tell them exactly what I think the issue is.

 

Any ideas? I appreciate any advice on the matter. I'm wondering if it just needs some more miles to loosen it up, but it seems pretty drastic.

[MikeNH]

Can't offer any advice on the 4WD but either turn off the sensors in bad weather or get used to false alerts. Just the nature of the beast.

[pm26]

Something is definitely wrong. 4-8 MPG is bad even for an old U Haul F350 truck with 460 cu in V8. When you leave the truck automatic 4 WD, this setting is supposed to eliminate unnecessary drag on the driveline due to engaged front axle when you alternate between slick and normal traction surfaces. Sounds to me like you have a defective transfer case that does not function as designed.

[Imcrazy]

Yeah that is terrible. I have a 4.3L 4x4, when I run 2wd around town I get 17-20 mpg, when I run 4x4 auto I get about 16-18 around town. I don't do much highway driving and rarely have used anything but 2wd on the highway. The only noticeable difference to my truck in auto 4x4 is the increased traction and acceleration.

[Isriam]

don't drive in auto unless you need 4wd. think of auto as auto 4 hi 4 low or something. you'll create excess drag on the transfer case if you don't need 4wd and wear it out. i pretend auto doesn't even exist.

[00Silverado4x4]

don't drive in auto unless you need 4wd. think of auto as auto 4 hi 4 low or something. you'll create excess drag on the transfer case if you don't need 4wd and wear it out. i pretend auto doesn't even exist.

Not exactly true, auto 4x4 is not just when you "need" 4wd. If that was true then you would just switch to 4wd. It actually tells you what Auto 4wd is for in your owners manual. It's for "variable" weather conditions. Also Auto 4wd only enables 4 hi when senses rear wheel sleep. It will not engage 4 lo for any reason. Yes you will take a loss of mpg's using the system but not nearly as bad as the OP is seeing on his truck. I've used mine extensively and never taken more than 1-2mpg loss. The system will not create "excess drag", again, if it did, GM would put a warning in the owner's manual regarding the use of the system.

[fondupot]

Driving in 4 auto will decrease mileage a bit, but not that much. There shouldn't be an excessive "dragging" feeling. Sounds like you have a locked up brake or something.

 

And about the proximity sensors, they will get activated by snow/ice accumulation, I've had mine will go off in the snow. I just turn them off when I realize it.

[TJay74]

don't drive in auto unless you need 4wd. think of auto as auto 4 hi 4 low or something. you'll create excess drag on the transfer case if you don't need 4wd and wear it out. i pretend auto doesn't even exist.

 

 

This info is not correct.

 

4wd Auto is for when conditions could be slick but you don't need to be in 4HI. It engages the clutches in the transfer case and the moment the truck sense wheel slippage it locks the transfer case fully just like in 4HI.

 

4HI should be used when driving on pure snow/ice/sand/gravel where you need full time 4wd.

 

Auto will not hurt a thing, I accidently drove my truck around for 2 weeks in 4 Auto and other than a slight gas mileage hit the truck drove fine and you couldn't even tell it was in Auto.

[Isriam]

 

 

This info is not correct.

 

4wd Auto is for when conditions could be slick but you don't need to be in 4HI. It engages the clutches in the transfer case and the moment the truck sense wheel slippage it locks the transfer case fully just like in 4HI.

 

4HI should be used when driving on pure snow/ice/sand/gravel where you need full time 4wd.

 

Auto will not hurt a thing, I accidently drove my truck around for 2 weeks in 4 Auto and other than a slight gas mileage hit the truck drove fine and you couldn't even tell it was in Auto.

 

I know for a fact, that Auto will break your transfer case, and when you take it to the dealer they will say yea, we know, don't drive in auto.

 

Put your truck in auto and then do a slow tight turn in a parking lot. You will hear all 4 wheels grab and release. The transfer case thinks your vehicle is slipping, grabs, then releases. You WILL break something by driving in auto for long periods of time. Not by driving 60 down the interstate in a straight line, but by daily city driving of turning into parking spaces, and anywhere else it will grab and put strain on the transfer case.

 

But do whatever you want, its your truck.

[00Silverado4x4]

 

 

Put your truck in auto and then do a slow tight turn in a parking lot.

I have, numerous times, on drive pavement. No grab or bucking.

May I ask where your facts come from about Auto? My facts are only based on my personal experience which is Auto has not harmed my transfer case for the 135k miles I have driven it. At least 25% of that has been in Auto in rain, snow, mud, dirt, pavement, gravel...etc, etc, etc.

[TJay74]

This is my 3rd GM full size truck with the electronic transfer case and have never had an issue using Auto when the roads are iffy. If they have snow/ice on them I am in 4HI.

 

All of my trucks have the G80 locker option on them from the factory, so the rears don't unlock unless you are turning and there is enough force to unlock the locker. The front diffs use a standard clutch diff as does the transfer case. Transfer case wont have much slippage to worry about since it is a straight in/out input shaft system.

[Isriam]

like i said, its your truck drive it how you want. i don't care if you break it, just don't complain here when you have tcase failure. consider yourself luck, kinda like not having a vibration issue.

[darkfox1]

If auto were so bad why would it even exist?

 

that being said, the whole "shift on the fly" system is fragile. I broke my encoder motor on my 2010 the 2nd time I used 4wd by shifting from 2wd to 4auto while doing a very VERY slight roll.

 

Now I always put the turck in neutral and come ot a full stop when changing.

 

Btw, I just drove auto4 this morning on my 14 mile trip to a client. It's been raining and the temp is dropping fast down here. This truck is like ice skating on wet roads.

 

I reset my trip meter, I got just about 16mpg on that trip, which was ~70mph the whole way. I did some stop/start tho for about 5 miles of that tho.

[pm26]

There are lots of vehicles out there today with permanent 4 wheel drive systems. Typically such a system utilizes a center differential to account for differences in traction between front and rear wheels to prevent tire scuffing and excessive driveline loading. An AUTOTRAC transfer case performs the same function as the center differential in permanent 4WD vehicles. The whole purpose of AUTO 4WD is engage and forget, when road conditions vary from slippery to good traction.

[KARNUT]

The last Z71 I had was in 2004, any time the road conditions became wet I hit auto 4wd. My trucks until just a couple years ago were off road all the time. I even used auto 4wd off road most off the time. The only time I didn't is when I needed low range in the mountains. I sometimes would use it when I wanted to take off at light flat out. I traded it in at 200k for a trailblazer ss, that should give you an idea how I drive. The only thing I did to that truck was back brakes and a water pump. I wish I could have cloned that truck.