Driving in 4x4 auto?

[PMattras]

While I agree with not running in Auto all the time you should still exercise the system monthly according to my GM Service manager. He recommended a few miles in auto with a little off road in 4H/4L time to keep things lubricated.

 

I don't have 4 wheel auto but I was told you should always pop it into 4 wheel drive once a month (short time) to keep things lubricated etc. as well.

[fondupot]

 

 

I don't have 4 wheel auto but I was told you should always pop it into 4 wheel drive once a month (short time) to keep things lubricated etc. as well.

 

I've heard this too. But I'm not sure how valid it is. Because the even when in 2wd the transfer case and front drive-line components are spinning from the wheels (the hubs are always locked), its just not engaged and receiving power from the motor. So they are being lubricated even when not in 4wd or AUTO.

 

That's how this system is able to function "on the fly." Everything is already moving and when you flip to AUTO the transfer case engages and now the front wheels receive power from the engine. And when you flip back to 2HI, the t-case disengages and unloads the front drive-line.

 

If the front drive-line components were stationary you would probably grenade the transfer case and front end from the force of going from a standstill to speed.

 

At least that's how I think it works, maybe we get a better 4 wheel drive techie in here to explain a little better.

 

At the least, I guess its good to test it once in a while just to make sure it works! The actuators in there need their exercise.

[thetruck454]

 

That's how this system is able to function "on the fly." Everything is already moving and when you flip to AUTO the transfer case engages and now the front wheels receive power from the engine. And when you flip back to 2HI, the t-case disengages and unloads the front drive-line.

 

I think that is where the confusion may be. Auto locks the front axle together, not the tcase. The clutch in the tcase is applied In a smooth manner to engage/disengage 4x4 in auto.

 

If the front drive-line components were stationary you would probably grenade the transfer case and front end from the force of going from a standstill to speed.

 

That is exactly true.

 

 

At the least, I guess its good to test it once in a while just to make sure it works! The actuators in there need their exercise.

they can stick from.not being used over time. Cycling them once in a while prolongs this.

[Silverado-Hareek]

I don't think you have to do it every month but a couple times a year is good. I hardly ever did it in my 2007 and never had a single 4WD problem in 100k miles before i traded it for the '14.

[KARNUT]

I did it every time it got wet, the take off was fun, most when there was a mustang next to me. Would have been more fun to get them to shift from low to high under full throttle.

[BR-TEXAS]

 

That is a different 4 wheel drive system all together. that was a true AWD. Whereas AUTO 4 in our trucks is a PART TIME 4wd system. Big difference.

AWD has a center differential.

[EaZ8]

NEVER NEVER NEVER NEVER DRIVE IN 4 Auto all the time unless you are on loose terrain that may require 4 wheel drive!!!!

 

4 Auto is not a luxury feature that lets the truck determine when you need 4 wheel drive. 4 Auto engages the front drive shaft but does not send power to the front wheels unless the truck senses slippage. The luxuriousness of this feature exists here where it allows the truck to only send power to the front wheels when needed for traction but you are still only supposed to use it in 4 wheel drive conditions. You can actually mess up your transfer case and front differential driving on hard pavement in 4 auto all the time. You should be in 2 wheel drive at all times unless conditions call for 4 wheel drive. When conditions do call for 4 wheel drive, then you need to determine if you need 4Hi for constant 4 wheel drive or if 4 auto is sufficient. I use 4 auto when there's say maybe an inch or 2 of snow on the roads. Otherwise if it's deep snow or sand I'm in either 4Hi or 4Lo. Otherwise you should be in 2 wheel drive for daily commuting and driving on hard pavement.

i useto have a 4x4 GMC jimmy with basically the same 4auto, 4hi,4low, and 2hi. i use to do exactly what you said here always run in 2wd unless there is a little snow in that case 4 auto and i use to drive on unploughed roads a lot which were sometimes 1 foot deep plus the snow drifts which is when i would lock it in 4hi.

one thing i didnt like about the 4 auto on the jimmy is it was really slow to respond which can really mess you up if the back end starts to slide (i may mix this up a bit because its been a few years but.,,) rwd you counter steer and stay on the gas to drift back in so you would start off like that then the 4 auto would respond and you have to change your counter steering to gas and point where you want to go.mind you i use to trigger it to do this on purpose sometimes so i got really use to it.

i took the sierra with 4 auto on a test drive when it had just dumped rain and the salesman told me to pin the gas so i did, rear end kicked out and he asked why i switched it to 2wd. threw it in 4 auto and i hav eto say the system is crazy responsive, i didnt feel the lag that my jimmy had in kicking in the front wheels traction it was just instant grip and go.

the salesman has his own sierra and he says he always drives in 4 auto all year round, he does lots of towing and lots of km per year (family friend so i know he isnt pulling my leg).

personally, im going to be running in 2wd unless i need the 4x4 on dirt or snow.

[chrisuns]

While I wouldn't drive in auto 24/7, as it causes the front differential to lock with the passenger side - increasing rotational resistance in the driveline, hence lower mileage. You won't hurt anything turning it on for play, rain etc. The mp3023 is a very stout case, it's used in several jeeps for full time intelligent awd and several performance lines. In fact, their's go through much higher stresses than what the GM TCCM commands of. E.g., performance based biasing 20/80, 30/70, 40/60. The only difference mechanically is the clutch plate has bearings that reside in ramps. Jeep's are 100% duty while GM's are not, leading to the occasional bearing failure after 50-100k miles of auto 24/7.

If you want to run auto 100% of the time, these bearings should be replaced with stronger units. On my 2500 I have a MP3024 that is heavily modified(bearings, added clutched and chain) to cope with 1400fts lbs daily; not worried one bit about it if I want to run it in auto 24/7.

[Silverado-Hareek]

 

Good to know. I figured something had to be different with the information given on here. Completely different transfer cases I assume?

 

 

 

Yes different transfer case and probably a different or modified front Differential.

 

 

Definitely a different front differential. An all wheel drive system is different than a 4 wheel drive system in that with all wheel drive the entire drivetrain is engineered to power all 4 wheels all the time. This is good for the average driver that just needs some traction in wet or light snow or sand conditions. If you really want to go off-road and handle more serious terrain like soft sand or deep snow, a 4wheel drive system with different gearing options is better suited for that. I'd argue most of us are fine with an all wheel drive system, but the non luxurious trucks are just built from the factory to work and handle more than one designed for a luxurious ride.

 

Everyone questioning our logic, put your truck in 4 wheel drive and then turn hard to the right or left and drive. You will feel a popping and a jumping/jerking to the truck.....that's the front tires opposing each other by spinning at different rates and not being on loose terrain to lose traction. In other words, it's terrible for the truck to drive in 4 wheel drive on pavement. Now 4 Auto won't technically do this all the time because power is only being sent to the front wheels when slippage occurs but the potential exists for that power to be sent if the truck senses any type of slippage for whatever reason.....some sand on the road in winter or rain or whatever the case may be.

 

Those that asked for evidence on why we think this isn't good, here are some thoughts I have:

 

1) If it was completely harmless, why not make Auto 4 wheel drive the base setting on these trucks from the get go? Why even have a 2 wheel drive option if it's un-necessary or you shouldn't be using it?

2) From the manual: "AUTO (Automatic Four-Wheel Drive): This setting is ideal for use when road surface traction conditions are variable. When driving the vehicle 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. Driving in this mode results in slightly lower fuel economy than Two-Wheel Drive High."

I did read the cautionary note about driving in 4HI or 4Lo on dry pavement but it said nothing about 4Auto so I will concede that point that the manual doesn't warn against it. But using my own logic, especially point #1 above, I won't be doing it in my truck ever. Feel free to do it in yours at your own discretion, but if someone were to ask my personal advice, I will always advise against it. That's just me.

[newdude]

 

 

 

 

 

Definitely a different front differential. An all wheel drive system is different than a 4 wheel drive system in that with all wheel drive the entire drivetrain is engineered to power all 4 wheels all the time. This is good for the average driver that just needs some traction in wet or light snow or sand conditions. If you really want to go off-road and handle more serious terrain like soft sand or deep snow, a 4wheel drive system with different gearing options is better suited for that. I'd argue most of us are fine with an all wheel drive system, but the non luxurious trucks are just built from the factory to work and handle more than one designed for a luxurious ride.

 

 

Front differential is the same no matter if its floor shift or the autotrac. Difference is in the transfer case.

[Silverado-Hareek]

 

 

Front differential is the same no matter if its floor shift or the autotrac. Difference is in the transfer case.

 

I'm talking about All Wheel Drive systems versus 4 wheel drive systems in the paragraph you quoted.

[KARNUT]

I had 200,000 miles on my 04 Z71 when I traded in, I put 410s in it had a tune cold air the works. When it rained or went off road ( I work in the off road arena)or just generally wanted more, it was in auto 4WD. Just driving on dry payment no it was to easy just to hit the button. The only thing I did to that truck was back brakes. Even had the same spark plugs, I use to drive a lot and hard, that was in just 30 months.

[Silverado-Hareek]

I had 200,000 miles on my 04 Z71 when I traded in, I put 410s in it had a tune cold air the works. When it rained or went off road ( I work in the off road arena)or just generally wanted more, it was in auto 4WD. Just driving on dry payment no it was to easy just to hit the button. The only thing I did to that truck was back brakes. Even had the same spark plugs, I use to drive a lot and hard, that was in just 30 months.

 

Not a fair comparison. They don't make trucks like they used to in '04. Back then they still made tanks with engines that didn't consume oil!

[MikeNH]

While I wouldn't drive in auto 24/7, as it causes the front differential to lock with the passenger side - increasing rotational resistance in the driveline, hence lower mileage. You won't hurt anything turning it on for play, rain etc. The mp3023 is a very stout case, it's used in several jeeps for full time intelligent awd and several performance lines. In fact, their's go through much higher stresses than what the GM TCCM commands of. E.g., performance based biasing 20/80, 30/70, 40/60. The only difference mechanically is the clutch plate has bearings that reside in ramps. Jeep's are 100% duty while GM's are not, leading to the occasional bearing failure after 50-100k miles of auto 24/7.

 

If you want to run auto 100% of the time, these bearings should be replaced with stronger units. On my 2500 I have a MP3024 that is heavily modified(bearings, added clutched and chain) to cope with 1400fts lbs daily; not worried one bit about it if I want to run it in auto 24/7.

 

The front diff doesn't lock. It's always open. Binding occurs because the transfer case forces a 50/50 spilt in modes other than auto, preventing a speed differential between front and rear axles.

[Silverado-Hareek]

The front diff doesn't lock. It's always open. Binding occurs because the transfer case forces a 50/50 spilt in modes other than auto, preventing a speed differential between front and rear axles.

I disagree here. The issue is the speed differential between the front left and right tires when turning because the front axle is spinning at a constant rate but when you turn say to the right, the left tire rotates more than the right tire. This isn't a problem under normal driving but when you are in 4wd and the truck is sending power to the front axle and wheels, binding occurs on dry payment when turning because the tires are rotating at different rates from each other while the front axle is driving both of them at a constant rate. That's why you have to be on loose terrain so the right tire in this scenario can slip and not oppose the left tire, and vice versa when turning to the left.