Auto mode turns on 4x4 mode

[intheburbs]

Do not use auto 4WD on pavement. You will destroy the front differential.

Not true.

Yes, driving on dry pavement in 4hi or 4lo is bad, but the Auto setting is specifically designed for any surface, any time. It simply puts the system into "standby."

From the owner's manual:

"AUTO (Automatic Four-Wheel Drive): This setting is ideal for use when road surface traction conditions are variable. When driving your vehicle in AUTO, the front axle is engaged, but the vehicle’s power is primarily sent to the rear wheels. When the vehicle’s software determines a need for more traction, the system will transfer more power to the front wheels. Driving int his mode results in slightly lower fuel economy than Two-Wheel Drive High."

 

[91RS]

Yes, true. Thank you for proving my point, I thought I was going to have to search the OM. Key word: variable. When traction conditions are variable. Pavement is not variable. If you use auto 4WD on pavement you will smoke your front differential, generally in the 60k-80k mile range but some will last longer but they will eventually need new bearings and sometimes gears.

 

[JohnnyParadis]

Just kinda curious why you feel the need to turn off stabilitrack and traction control every time?

I can't say for sure how the Auto 4wd system detects wheel slippage to engage the transfer case, but I'd wager it uses the sensors from one or more of those systems, so with the fuse out the result is the transfer case engaging in "auto."

Up here in extreme Northern Maine (google 04756...) many roads are ice covered for 4-5mths a year and we get allot of snow that doesn't melt and just piles up until Spring. I've been running separate winter tires and rims for 30+ years (usually, Nokian's best studded tires) and this is the first vehicle I own that negates the tires. I've ditched it twice with this 9 year old (to me) Tahoe, because the "traction control" &/or "anti-slip braking", took away control of the vehicle from me. So...every time I leave the garage (usually to greet a good-size bank or at least glare ice) at my mailbox...) I have to hold the TSC button, and wait for 10 seconds until the indicator lights show it's all off, before leaving. Just don't like waiting for something tha's dangerous, and impedes my progress. Sorry for the rant, been waiting a while to let it out, cheers.

 

[wjburken]

Yes, true. Thank you for proving my point, I thought I was going to have to search the OM. Key word: variable. When traction conditions are variable. Pavement is not variable. If you use auto 4WD on pavement you will smoke your front differential, generally in the 60k-80k mile range but some will last longer but they will eventually need new bearings and sometimes gears.

The front differential is an open differential so differences between the front wheel speeds shouldn’t matter. If the transfer case isn’t engaged with the front drive shaft, there isn’t an issue there.

The fact of the matter is Auto4WD is designed to be used in situations where you “may” encounter adverse road conditions which means mostly dry road conditions with possible sections that are not.

 

[wjburken]

Yes, true. Thank you for proving my point, I thought I was going to have to search the OM. Key word: variable. When traction conditions are variable. Pavement is not variable. If you use auto 4WD on pavement you will smoke your front differential, generally in the 60k-80k mile range but some will last longer but they will eventually need new bearings and sometimes gears.

The front differential is an open differential so differences between the front wheel speeds shouldn’t matter. If the transfer case isn’t engaged with the front drive shaft, there isn’t an issue there either.

The fact of the matter is Auto4WD is designed to be used in situations where you “may” encounter adverse road conditions which means mostly dry road conditions with possible sections that are not.

 

[91RS]

The front differential is an open differential so differences between the front wheel speeds shouldn’t matter. If the transfer case isn’t engaged with the front drive shaft, there isn’t an issue there.

The fact of the matter is Auto4WD is designed to be used in situations where you “may” encounter adverse road conditions which means mostly dry road conditions with possible sections that are not.

Since you’re apparently the engineer, why do most of the front differentials go bad at such low mileage then when auto 4WD is used but not when people keep it in 2WD on pavement? This is a known issue with the older AWD trucks and the trucks with auto 4WD. Search around here and whenever someone has a noise the front differential is the second thing they’re told to check after the wheel bearings. There are tons of posts, YouTube and TikTok videos talking about this.

The auto 4WD system was NOT designed for that. The owners manual literally says only to use it in variable traction conditions which is off-road (read: not pavement). The only time it should be use on pavement is in snow/ice.

 

[wjburken]

Since you’re apparently the engineer then why are all the front differentials going bad at such low mileage then when auto 4WD is used but not when people keep it in 2WD on pavement?

The auto 4WD system was NOT designed for that, nowhere does GM say that’s what it was designed for. The owners manual literally says only to use it in variable traction which is off road and snow/ice.

I don’t see “Off Road and Snow/Ice” in the manual either. I guess we just share different understandings of what “Variable” means, which is fine with me.

I’m basing my understanding on my understanding of how the drivetrain is designed along with how it was explained to me almost 20 years ago by a very long time family friend that was like a 2nd dad to me and who owned the local Chevy dealership when I bought my 2005 Silverado with Auto4WD.

Would I recommend driving in Auto4WD in the heat of summer? Nope. Did my wife do it on a regular basis when she was driving a non-AWD Suburban? Yep! Did it toast the front diff? Nope. Did it tell her to knock it off? Yep!

That being said, I don’t think the rate of front differential failures is much higher than the failure rate of rears, based on what I’ve seen here on the forum.

Personally, I think most of the front differential failures, as well as many of the rear failures, are due to poor maintenance and not changing the gear oil often enough.

 

[intheburbs]

Yes, true. Thank you for proving my point, I thought I was going to have to search the OM. Key word: variable. When traction conditions are variable. Pavement is not variable. If you use auto 4WD on pavement you will smoke your front differential, generally in the 60k-80k mile range but some will last longer but they will eventually need new bearings and sometimes gears.

I'm not going to get into a ******* contest. You're misinterpreting the word variable to mean varying levels of low traction, when the intent is for any range from normal (dry) traction to low traction.

Auto 4wd is designed for situations where you MIGHT encounter bad traction conditions. You're not going to get tire scrub while in Auto, because the front diff is still unpowered. Only when the vehicle detects slippage does it actually engage the front diff. Perfect example is plowed roads where there's a chance you might encounter an unplowed road or drifting/blowing snow.

If you're driving in variable low-traction conditions , then just put in 4hi.

 

[George B]

@91RS the front diff is the same in the 4x4 and AWD trucks with the only difference being the 4x4 version has a disconnect and the AWD is always engaged. They go bad because of crappy bearings or failed adjusters. Not because they are engaged. Many of them go over 100k before they fail in bot iterations.

Edit: Not trying to be a smart **** or captain obvious.

 

[George B]

I will add that the part time transfer case is also probably not meant to be in auto mode all the time.