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Discussion Starter · #1 ·
Hey guys.

Took a camping trip into the mountains of Virginia this weekend. Drove probably 500+ miles with my truck in 4 hi mode and did not even realize it until I pulled in my driveway. I live in a fairly muddy area so I usually have to put 4x4 on to pull in my driveway and must have forgot to switch it offI have a 2016 Chevy Colorado for reference.


About 200 or so of the miles were on slick roads if that helps, I just am wondering what I should be doing/checking for. I’m hoping I avoided major damage. A lot of the roads were curvy as well as I’m going up and down mountains. The speeds along the mountains were about 25-40 mph. I drove straight on the highway for the most part reaching a top speed of about 80 mph. If anyone could calm the nerves that would be great, just pretty worried as I have not had the truck very long and would hate to have to shell out a major repair so soon.

Any advice would be appreciated! P.S. does 4x4 mode always stay on even after the truck is turned off and turned on? I thought I read somewhere that sometimes the light will show as 4x4 hi but it is just in 2wd. Any insight would be appreciated. Thank you!
 

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I did the same thing 2 years and 25,000 miles ago, mine was 425 miles and I wondered why I was not getting good gas mileage. Have not had any issues and have used the 4wd quite often
 

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I don't believe you would have done any damage. Your diffs were still in the same state they would have been in 2HI. You might have put some unnecessary heat/wear on your front output shaft and seal, but I imagine they have a life of more than what you drove.

If you wanna treat her real nice, you could always replace the fluid in your diffs and transfer case similar to changing the oil in the engine after a long road trip.
 
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I don't think there is anything specific you need to do about what has already happened. I'd just keep an eye on it in the future.
Regarding it turning off when the ignition is off... No. It doesn't do that. The selector is a switch (by the light). So, wherever you have it rotated to, is where it stays until you move it. I have to watch mine as I often hit mine with my knee when I get in. I always just glance to see if the indicator is lit up. I have always just knocked it into 4 auto.

I do believe the front and rear lockers (ZR2) will disengage after off/on cycle.
 

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I don't think there is anything specific you need to do about what has already happened. I'd just keep an eye on it in the future.
Regarding it turning off when the ignition is off... No. It doesn't do that. The selector is a switch (by the light). So, wherever you have it rotated to, is where it stays until you move it. I have to watch mine as I often hit mine with my knee when I get in. I always just glance to see if the indicator is lit up. I have always just knocked it into 4 auto.

I do believe the front and rear lockers (ZR2) will disengage after off/on cycle.
If the 4WD switch is moved with the ignition off then it will NOT change modes when the ignition is turned on. There are actually 2 indicator lights on the 4WD switch, the white indicator that shows the selected mode and then a smaller, dimmer amber light that shows the active mode. The switch isn't a normal switch, it actually sends a different signal to the computer when the knob is turned to a different position and that signal is what triggers the mode change. With the ignition off when turning the knob there is no signal sent to indicate the mode change and so the mode doesn't change when the truck is started. The switch will blink the amber LED if the selected mode doesn't match the active mode.

As such, hitting the knob and switching it to 4WD with the ignition off has no risk.

To the OP, aside from wear on various components the biggest risk is cracking the transfer case due to high torque load and lack of wheel slip to release it. Seen it happen with someone else's vehicle.

I would also question whether or not it was really in 4H or not. Did you have it in 4H and forget to shift out or did you notice the switch was in 4H and figured it must've been bumped? It's usually pretty obvious if you're in 4H on pavement, but I can see under certain conditions it being something that might not be noticed. If the knob was inadvertently turned with the ignition off then see above, it wouldn't be in 4WD. When you turn the key off it remains in the mode selected and doesn't change. If it's in 4H it remains in 4H until the mode it switched again with the ignition on or engine running.

If you're not noticing any issues then there's not much for you to do now, just drive it. Any damage would either have been excessive wear on components, shorting their life, or excessive driveline wind-up resulting in catastrophic failure of one of the components.
 

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Ive hit the knob unknowingly a few times and ended up in 4hi, so easy to do on ingress and egress, and since our 16’s dont have an indicator light on the dash, its hard to see when you have. Dumbest switch layout ever. Same thing happens with the headlight knob, but the dic tells you when it happens.
 
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Ive hit the knob unknowingly a few times and ended up in 4hi, so easy to do on ingress and egress, and since our 16’s dont have an indicator light on the dash, its hard to see when you have. Dumbest switch layout ever. Same thing happens with the headlight knob, but the dic tells you when it happens.
"since our 16’s dont have an indicator light on the dash"

What do you mean by that ?
 

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"since our 16’s dont have an indicator light on the dash"

What do you mean by that ?
There's no dash indicator showing that the truck is in 4WD, only a momentary indication on the DIC showing a mode change in progress. If you want to know if it's really in 4WD then you have to look at the 4WD knob and then make sure the amber LED matches the selected mode.
 
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"since our 16’s dont have an indicator light on the dash"

What do you mean by that ?
Starting in i think 2018 or 2019, the dash near the speedo/tachometer has a green indicator light that lets you know when the transfer case is in anything but 2wd. So it will illuminate when in AUTO, 4hi and 4lo.
 

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To the OP, aside from wear on various components the biggest risk is cracking the transfer case due to high torque load and lack of wheel slip to release it. Seen it happen with someone else's vehicle.
are you saying our trucks are like the older trucks that had 4:10 in back and 4:11 in front?
In shich yoou would get spring rap and teat up u-joints and transfer cases cause something would havee to give at 70mph with the front a back going at different speeds.
On my 74 PowerWagon the front end would bounce due to the different gear ratios

If so I would have 3:42 in back and 3:43 in front and guys swapping gears will have 4:10 and 4:11's but all I hear/read is guys installing 4:10's
 

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There's no dash indicator showing that the truck is in 4WD, only a momentary indication on the DIC showing a mode change in progress. If you want to know if it's really in 4WD then you have to look at the 4WD knob and then make sure the amber LED matches the selected mode.
Ahh, yeah, that checks. I always thought it odd that we can pause and rewind live radio but heaven forbid GM show you what your tranfercase is in other then the tiny LED on the knob.
 

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are you saying our trucks are like the older trucks that had 4:10 in back and 4:11 in front?
In shich yoou would get spring rap and teat up u-joints and transfer cases cause something would havee to give at 70mph with the front a back going at different speeds.
On my 74 PowerWagon the front end would bounce due to the different gear ratios

If so I would have 3:42 in back and 3:43 in front and guys swapping gears will have 4:10 and 4:11's but all I hear/read is guys installing 4:10's
Nope, nothing to do with gearing. Differences in tire diameter due to differences in wear as well as tires traveling different distances when making turns because each tire takes a different path causes driveline wind-up/binding because each tire wants to travel at a different speed. The front tires are tied to the rear tires due to the transfer case being locked in 4H or 4L. When you make a turn, the front tires travel farther than the rear tires, if they weren't tied to the rear tires they would rotate faster than the rear tires. However, since they're locked to the rear tires the front differential input speed has to match the rear differential input speed, this means tires have to scrub, hop, slip, etc and if they can't then the torque builds in the driveline until it can be released, either by turning in the opposite direction, wheels being able to slip, or something breaking. Various parts in the driveline have a certain amount of give, while they seem rigid to our hands they're not when subjected to the actual forces from driving. Driveshafts can twist slightly, axle shafts can twist slightly, etc. The bucking, chirping, etc you hear when using 4H/4L on hard surfaces is that built-up energy being released.
 
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Nope, nothing to do with gearing. Differences in tire diameter due to differences in wear as well as tires traveling different distances when making turns because each tire takes a different path causes driveline wind-up/binding because each tire wants to travel at a different speed. The front tires are tied to the rear tires due to the transfer case being locked in 4H or 4L. When you make a turn, the front tires travel farther than the rear tires, if they weren't tied to the rear tires they would rotate faster than the rear tires. However, since they're locked to the rear tires the front differential input speed has to match the rear differential input speed, this means tires have to scrub, hop, slip, etc and if they can't then the torque builds in the driveline until it can be released, either by turning in the opposite direction, wheels being able to slip, or something breaking. Various parts in the driveline have a certain amount of give, while they seem rigid to our hands they're not when subjected to the actual forces from driving. Driveshafts can twist slightly, axle shafts can twist slightly, etc. The bucking, chirping, etc you hear when using 4H/4L on hard surfaces is that built-up energy being released.
Yeah, I knew all of that, just what you were saying to the op when he was on the higway at 70mph for 500 miles experiencing all of that....thought maybe I missed that our trucks were like the old style with different gearing
 
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Yeah, I knew all of that, just what you were saying to the op when he was on the higway at 70mph for 500 miles experiencing all of that....thought maybe I missed that our trucks were like the old style with different gearing
Gotcha, nope. You could drive 500 miles on a perfectly straight road in 4WD and still break something because of the irregularities in tire sizes, road surface, etc. You could also get lucky and not break anything. You could also end up stretching the chain in the transfer case that results in chain slap and jumping teeth when in 4WD. The aluminum t-case housing and aluminum front diff housing can be the weakest links depending on the loads put on them. For example, using the front tow hooks to try and get a vehicle unstuck by tugging them out in reverse can crack the front diff housing, not due to binding of some sort but because of how the hypoid ring and pinion gears work (drive side vs coast side and what the gears do when torque is applied to one side vs the other, which is what happens when going forward vs reverse).

Not suggesting our trucks are fragile, just it's not always obvious what's at work and why certain things are bad. The front tow hooks are to have the truck towed, not for towing another vehicle or tugging something like a tree stump in reverse, for example. I'd say most people don't know that and then want to blame the truck or the manufacturer when their front diff grenades.
 

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I did this in my 02 avalanche. It was about 100 miles on hot dry asphalt over stevens pass fully loaded for camping at average of 55. Middle of summer so probably 80-90f. No issues. I know it’s a different running gear entirely but I would just expect it to be fine. Also forgot to switch that truck from auto to 2wd a hundred times coming off of different snowy areas and off road spots. You can usually feel the drag in The drivetrain especially in 4Hi and sometimes you get a little more torque steer.
 
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Discussion Starter · #16 ·
Thank you guys for the insight.

I live near a culdesac, so I drove up there and flipped the truck to 4WD and did a slight turn, I could feel the lurching some were describing and immediately flipped back to 2WD and all was well. Feeling this lurching makes me think I might have just accidentally bumped the knob with the ignition not engaged so really it was showing as 4WD but was indeed just in 2WD.

I will definitely only use 4WD when there is snow or ice and will always be sure to check before I get in to make sure it is in 2WD after this experience. Hoping I didn’t do any serious damage and the truck lasts a while!
 

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Gotcha, nope. You could drive 500 miles on a perfectly straight road in 4WD and still break something because of the irregularities in tire sizes, road surface, etc. You could also get lucky and not break anything. You could also end up stretching the chain in the transfer case that results in chain slap and jumping teeth when in 4WD. The aluminum t-case housing and aluminum front diff housing can be the weakest links depending on the loads put on them. For example, using the front tow hooks to try and get a vehicle unstuck by tugging them out in reverse can crack the front diff housing, not due to binding of some sort but because of how the hypoid ring and pinion gears work (drive side vs coast side and what the gears do when torque is applied to one side vs the other, which is what happens when going forward vs reverse).

Not suggesting our trucks are fragile, just it's not always obvious what's at work and why certain things are bad. The front tow hooks are to have the truck towed, not for towing another vehicle or tugging something like a tree stump in reverse, for example. I'd say most people don't know that and then want to blame the truck or the manufacturer when their front diff grenades.
The weakest link in the drive train is tires. Energy that supposedly is stored in the steel-hard gears of the drive train is expended through tire slip. The tire scuffs the pavement as it breaks traction at speed. You just don't here it. I used to train cross-country running along the highway at distances of 10 to 16 miles. The tires on vehicles were 3 to 5 feet away. When cars passed and hit chuck holes or high spots in the pavement, I would hear the tires scuff as the wheel(s) became "unsprung", losing their grip on the road surface. The scuffing noise was especially loud when vehicles hit a short hill. Sometimes when crossing a short hill at highway speed, you feel your butt trying to leave the seat. When that happened, your tires became unsprung, made a scuffing noise, and released any stored up energy. This happens to all vehicles, not just 4 wheel drives. IMO, the black tire marks left by semis on a highway bump are not caused by the driver hitting the brakes precisely at the second he/she hits the bump. The marks are created by the tire scuff and the driver wasn't playing with the accelerator or brake pedals.
 

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The weakest link in the drive train is tires. Energy that supposedly is stored in the steel-hard gears of the drive train is expended through tire slip. The tire scuffs the pavement as it breaks traction at speed. You just don't here it. I used to train cross-country running along the highway at distances of 10 to 16 miles. The tires on vehicles were 3 to 5 feet away. When cars passed and hit chuck holes or high spots in the pavement, I would hear the tires scuff as the wheel(s) became "unsprung", losing their grip on the road surface. The scuffing noise was especially loud when vehicles hit a short hill. Sometimes when crossing a short hill at highway speed, you feel your butt trying to leave the seat. When that happened, your tires became unsprung, made a scuffing noise, and released any stored up energy. This happens to all vehicles, not just 4 wheel drives. IMO, the black tire marks left by semis on a highway bump are not caused by the driver hitting the brakes precisely at the second he/she hits the bump. The marks are created by the tire scuff and the driver wasn't playing with the accelerator or brake pedals.
As soon as I posted this, I thought of a simpler explanation. When I dumped the cluch on my SS 454, 4 speed Chevelle, the least of my worries was the gears. The 12 inch rear tires would grow around 1 inch in diameter and I smiled with joy as the tires left their mark on the asphalt and acrid blue smoke filled the air. I didn't have to tear up the tires - I wanted to - never worried about breaking a gear. Tires are a good way to expend energy. The second weakest link in the drive train was the clutch, not the gears. However, I wouldn't recommend using 4WD when not needed.
 

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And yet people have blown diffs or snapped axles repeatedly by dumping the clutch when the tires have too much grip. I appreciate you trying to explain why it's not a problem due to tires, but I can assure you experience from countless people says otherwise. I've been doing this for a long time and I've seen the damage that can be done by using part-time 4WD on pavement. I've heard the damage, too. U-joints can be quite loud when they let go with a bang.

Tires won't slip enough to save the drivetrain if driven long enough.

Sent from my SM-G986U using Tapatalk
 

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And yet people have blown diffs or snapped axles repeatedly by dumping the clutch when the tires have too much grip. I appreciate you trying to explain why it's not a problem due to tires, but I can assure you experience from countless people says otherwise. I've been doing this for a long time and I've seen the damage that can be done by using part-time 4WD on pavement. I've heard the damage, too. U-joints can be quite loud when they let go with a bang.

Tires won't slip enough to save the drivetrain if driven long enough.

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I've been driving 55 years and owned 51 vehicles - no axle or gear issues. Ten years at a Chevrolet dealership - no gear issues. One axle issue. A Chevrolet Vega jacked up with 10 inch wide wheels stripped the splines because the wheels wouldn't slip. The Chevy rep refused warranty repair. The tire will slip well before an axle breaks in this situation - simple physics. Axles break for other reasons. However, I cursed myself liberally when I inadvertently put truck in 4 Hi. Rhetorical question: In 100,000 miles how many miles does the front differential have on it? I wouldn't be happy that I dove 500 miles on dry pavement but I wouldn't lose any sleep over it either.
 
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