[rfarhm]

Hi folks,
Yesterday I needed to pull my trailer out of the snow. I went to put the truck into 4 high, to my horrors it was already in 4 high. I have no idea how long. I don't know if I forgot to take it out of 4 high last time I needed it or if I hit it with my knee without noticing. I know when you're in 4 low, higher engine RPMs aside, just by the way the steering behaves there's NO WAY you could drive it on dry pavement without noticing the effects. I have to say, in recent driving, I've noticed no difference in behavior of the truck. So if it has been in 4 high for a while, I would have to say there's no clear difference in driving/steering. I know if you hit the knob by accident with the truck off into 4 WD, it will not switch over when you start the truck; it stays at the last setting. If it actually has been in 4 high, it could actually be more than 1,000 miles since the last time I know it shifted into 4 high. I'm not a dumb-ass. I know the 'feel' of my equipment. Is it possible I could have actually been in 4 high all this time without feeling it? If so, how much damage if it's actually been over 1,000 miles? A few times when I've pulled it into the garage after a long highway ride, I've noticed a subtle burning rubber smell I've never been able to localize on. Now I'm wondering if there's a connection. I love this truck and I'm freaking out a bit. Thanks for the opinions!

 

[rfarhm]

OK, I answered my own question with an experiment - so I'll post it here in case it's helpful for someone in the future...

I pulled into my snow-pack driveway. I did a right angle backup, going to full steering lock, like pulling out of a driveway with the windows open. The temperature is 10 degrees F and the snow is therefore quite sticky. I did four tests (sorry, I'm an engineer, what can I say...):

1. 2WD - the truck backed smoothly, just letting off the brake idling.
2. AUTO - the truck backed smoothly, just letting off the brake idling.
3. 4 LOW - as soon as I started to turn the steering wheel, had to apply gas otherwise the truck just stopped against the idling power of the engine. Audible chattering of the tires over the snow. The truck shuddered.
4. 4 HIGH - EXACTLY the same as 4 LOW.

I then went onto dry pavement for the final experiment. Nosed into a parking a space. Put the truck into 4 HIGH and began a right angle backup. IMMEDIATELY the truck felt like the brakes were applied and the attitude of the truck started to change as it tried to jack against the drivetrain tension. Obviously at this point I wasn't about to create damage so I immediately stopped and took it out of 4WD.

Conclusion: For this particular truck, I would have to be completely unaware and dumb as a stone to have had it in 4WD (high or low) on dry pavement and not notice immediately upon any kind of a sharp turn, let alone 1,000 miles. I'm relieved.

As a alluded to, I'm no Einstein but I'm not a dumb-ass either...

 

[mrbones]

Iirc, I don't feel a difference between Auto and 4H. I can only tell that I am in 4H during sharp turns, have yet put it in 4L.

 

[Skrow]

Iirc, I don't feel a difference between Auto and 4H. I can only tell that I am in 4H during sharp turns, have yet put it in 4L.

Does anyone's drive train seem to make a little more noise in the front going from 2WD to 4WD? Seems like when I shift into 4WD and going down the road, the front end seems to have more noise to it.

 

[Chevrolet Customer Care]

Hi folks,
Yesterday I needed to pull my trailer out of the snow. I went to put the truck into 4 high, to my horrors it was already in 4 high. I have no idea how long. I don't know if I forgot to take it out of 4 high last time I needed it or if I hit it with my knee without noticing. I know when you're in 4 low, higher engine RPMs aside, just by the way the steering behaves there's NO WAY you could drive it on dry pavement without noticing the effects. I have to say, in recent driving, I've noticed no difference in behavior of the truck. So if it has been in 4 high for a while, I would have to say there's no clear difference in driving/steering. I know if you hit the knob by accident with the truck off into 4 WD, it will not switch over when you start the truck; it stays at the last setting. If it actually has been in 4 high, it could actually be more than 1,000 miles since the last time I know it shifted into 4 high. I'm not a dumb-ass. I know the 'feel' of my equipment. Is it possible I could have actually been in 4 high all this time without feeling it? If so, how much damage if it's actually been over 1,000 miles? A few times when I've pulled it into the garage after a long highway ride, I've noticed a subtle burning rubber smell I've never been able to localize on. Now I'm wondering if there's a connection. I love this truck and I'm freaking out a bit. Thanks for the opinions!

Good Morning rfarhm,

We can see that you are seeking the input of other forum members, so we would like to offer our assistance as well. Our team would be more than happy to discuss this current concern with you. If this is something of interest, go ahead and send us a private message so that we may begin. Thank you and we look forward to hearing from you.

Best,
Philip J.
GM Customer Care

 

[Rogerwh0]

I had that same experience when I picked mine up from the dealer. I drove about 200 miles towards home before noticing that it was in auto. I definitely notice a noise when it is engaged now that I know the difference. The noise and vibration in 4wd is extremely annoying to me. I have been told it is "normal". I have a different opinion of normal apparently. I really wish GM had put some form of indicator in the dash to alert you it is in 4wd especially when the dial to engage it is behind the steering wheel and not visible without special effort.
I think the smell is the exhaust, when it regens the heat does make the exhaust smell. I have several other diesels and you can always smell it after a recent burn off.

 

[Timmydegs]

Same problem. Done it 2-3 times where I look down and wtf? Frustrating... even had it in 2wd once and went to park and acted as if it was in 4wd but knob was set to 2wd. Must have switched it back and forth with my knee without noticing.

The knobs are positioned right at knee level so it's easy to hit them without noticing. Done it with both the 4wd and lights. Even thought about putting some tape over them.

 

[Canyon 212]

The rubber smell I got to......dont know why...I was in all wheel mode....when I pulled in Garage...Didnt get the odor again....

 

[Rockcrawlerdude]

I've rebuilt a few older gm auto transfer cases and had a few with the auto 4x4. You can drive in 4auto all the time, but not in 4hi.
Here's how they work.
2wd: front axle disconnected
4auto: the front axle engages and the front axle is ready to take torque from the transfer case. When the truck detects the rear tires slipping it'll clutch in torque to the front axle. There is a clutch motor on the shift rail and a pack of ten clutch discs and nine friction discs (or vise versa). It can give up to 50/50 but if the truck moves and gets going the power will go back to the rear tires.
4hi: front and rear driveshafts both get equal power, non differentiated (binds on hard ground while turning)
4lo: front and rear both get equal power like 4hi but thru a low range planetary gear set

The negative to running 4auto all the time is that you are now spinning a front driveshaft which, agurably, adds wear and also an extra 40lb you are spinning all the time. Keep her in 2wd until you need 4.

Tim

 

[Rockcrawlerdude]

The rubber smell I got to......dont know why...I was in all wheel mode....when I pulled in Garage...Didnt get the odor again....

We don't have an "all wheel mode" the smell was likely during a regen, they stink.

 

[D&S]

I just found out last week that I have been in 4whl auto probably since our last snow in January. I do wish there was an indicator on the dash. The dial behind the steering wheel is never observed.

 

[Rockcrawlerdude]

I just found out last week that I have been in 4whl auto probably since our last snow in January. I do wish there was an indicator on the dash. The dial behind the steering wheel is never observed.

It's alright. You didn't hurt anything.

 

[Burgess159]

I guess I haven't put it in anything buy 2 wheel yet. I would have thought that there would have been a dash indicator telling you that it was in 4 auto, 4 high or 4 low or just 4x4. Thats unfortunate.

 

[Rockcrawlerdude]

Definitely no dash light. Mine was in auto when I picked it up at the dealer. It's fine to leave it in auto all the time. When your rear tires slip, it'll clutch in the front drive as needed.

However, I recommend using 2hi whenever you're on the road unless it's snowing or something. I've heard that snow stuff exists.

I say this because In 4auto you'll be unnecessarily spinning your front driveshaft which weighs probably 40 lb, may see a little difference.

Remember 4auto is rear wheel drive until you spin the rear tires then it sends some power to the front temporarily

 

[smthng]

I've done this numerous times... it seems to be mostly when getting in or out. Knee hits knobs, voila, random 4WD mode. Usually it's just Auto, so no big deal. But I've developed a habit of checking it when I stop. Now I don't think about it, I just turn the knob when I take out the keys.

BTW... if you get standing road water after rains, Auto is great for that.

 

[Miket8909]

My dad does the same thing and hits the knob with his knee when I let him drive my truck. I can tell right away as a passenger when 4wd is engaged but yet, poor location for the control knob

 

[BnLdamaxs]

I drove mine about 10miles normal highway speeds in 4high, someone else left it in 4high

 

[DKinney]

I've noticed a drop in fuel economy when in 4 auto which makes sense. And I agree with everyone else that they could've added some sort of indicator on the dash showing what the knob was set on. There's an indicator for the shifter position. I have also hit the knob with my knees and now I check it frequently.