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Transfer case leaves in "Auto" mode

21K views 42 replies 26 participants last post by  TopGun 
#1 ·
Hi,

Living in the north I left my transfer case in auto mode for the last couple months (since I bought it). I am curious if it'll hurt anything because the manual said the front axle is engage, just no power to it unless it's needed. The thing is up here the main streets and the highway are fairly clean and dry. Mostly just the side streets and roads less traveled are icier. I'm new to 4WD system (Subarus for last few cars) and don't want to damage any components.
 
#3 ·
I have had mine in Auto for 2 months now, i will just leave it there till spring thaw. Can't hurt anything.
My fuel economy had dropped, but this is due to many factors from winter blend fuel, winter tires, elevated idle running, and been freezing here for over a month. But i am still getting 26 mpg ( 9L/ 100kms per tank down from 30mpg ( 7.8L/100kms)in the summer. Fantastic for winter. My buddies V6 Coloroado has dropped to 17 mpg (13.8L/100kms) from his usual summer MPG of 22.
 
#5 ·
Your comment is correct. BUT....

It's winter. Roads have been wet,icy,snowy for awhile now. This is the nice feature of the AutoTrac option, you set it and forget it when there is any chance of traction loss. If we all waited to activate 4x4 when slippery then there would be no use for Autotrac. I like to be able to drive in the winter and not have to select 4x4 every time encounter a snowy/icy patch and not have to switch back to 2wd on sharp turns so axles don't bind.
 
#6 ·
^^^Yep. And in Auto, the truck will be in 2WD unless the rear wheels start to spin, then power is sent to the fronts.
 
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#7 ·
I noticed under hard acceleration the truck sounds different in Auto, almost like it has an exhaust. I couldn't figure it out until I looked and saw that I left in auto since the last snow storm. I can only surmise that the front axle is engaging for improved traction, even though I'm not getting any rear wheel spin.
 
#13 ·
If you run it in auto and the computer is frequently engaging the transfer case clutches it will cause accelerated wear, in a few years parts will need to be replaced.

I would rather put it in 4wd as required by myself when the wheels are not spinning and there is no shock to the driveline when the clutches engage.

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#14 ·
Whatever, you guys are overthinking/worrying about this. The Autotrac was designed to be selected and used . Its a well built system , use the option if you have it, that why it is there. I had autotrac in my 2002 Silverado 1/2 ton, put 350,000 kms on it used autotrac for 3 months at a time during winter, never had a single issue with the transfer case or front axle/diff assembly. If my truck has an option to select auto sensing 4wd, i sure as hell am going to make use of it. These trucks are not made of glass, use them for what a truck is to be used for.
 
#15 · (Edited)
Ya, won't hurt anything. It's designed to be used. Ironic it's called "auto". On the other hand, no reason to have it on in perfect weather on roads. Was going to start my own thread but this should work. Mine makes a loud growling noise when in AUTO and a severe vibration can be felt in the floor boards when accelerating. Is that normal? I'd assume a little noise but it's pretty loud and the vibration feels ugly like someone forgot to put the gear oil in the transfer case.
 
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#23 ·
Whatever drivetrain you leave your truck in, I wish there was a dash light indicator that showed if you were in 4WD... The dial is in a crappy place and hard to see. Heck the they have a light for everything else... perhaps the ran out of space...
 
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#25 ·
Last year i put mine in auto 4wd in october and switched back to 2wd in March, had zero issues, and i doubt any extra wear and tear. Same this year, been in auto 4wd for 2 1/2 months, won't put into 2wd till spring, that is the benefit of the auto, set it and forget it, there will be no ill effects from doing so. Did the same on my 2002 1/2 ton, left it in auto 4wd all winter, and ran it for 200k miles with zero 4wd issiues.
I think some worry too much about it, when your on dry pavement, the auto 4wd isn't engaging until slip is detected, can't hurt a thing.
 
#29 ·
Here's interesting article from Gears about the MP3010 transfer case, which is similar to the MP3025 and was used in GM full sized trucks. It gives a very detailed description of how the unit functions and how it is controlled.


https://gearsmagazine.com/magazine/magnas-mp-3010-transfer-case/
This article also provides similar info but for the transfer-case/system specific to our trucks, which Magna calls "Ultimax."

https://autotechreview.com/componen...deep-dive-into-magna-s-powertrain-innovations
 
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#31 ·
I usually leave it in 2wd in good weather but I'll put it in auto if I'm pulling out of a neighborhood onto a busy road otherwise half the time the rear end breaks loose and I chirp the tires as I step on it to quickly merge into 50mph heavy traffic from a dead stop. Auto instantly engages the front and keeps that from happening. I drop back to 2wd once I'm merged.

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#33 ·
So I asked the dealer this exact question and they looked at me as if I had 4 heads. "YOU DID WHAT IN THE HEAVY RAIN"???? I told him I looked in the manual and it said something like "Auto when traction is questionable". I forget the exact verbiage. So I contacted Chevy, and they referred me to the manual. I asked they exactly what questionable traction was and they kept referring me to the manual. Round and round and round we went....
 
#34 ·
Ok folks... here's my info about the Autotrac option. I have a 2017 Diesel and when I bought it the salesman said oh it's fine to leave it in all the time. No problems.

I've been in for warranty work 3 times with a squeel in the front driver wheel at low speeds. The service rep asked specifically if I had the autotrac engaged, which I did. He told me on dry conditions it should not be used.

My warranty repair was to the front output shaft and seal, premature wear out. Each time after about 5 months the squealing came back.

Luckily warranty is still good.

That's what happened to me, 2wd for me unless.....
 
#35 ·
Ok folks... here's my info about the Autotrac option. I have a 2017 Diesel and when I bought it the salesman said oh it's fine to leave it in all the time. No problems.

I've been in for warranty work 3 times with a squeel in the front driver wheel at low speeds. The service rep asked specifically if I had the autotrac engaged, which I did. He told me on dry conditions it should not be used.

My warranty repair was to the front output shaft and seal, premature wear out. Each time after about 5 months the squealing came back.

Luckily warranty is still good.

That's what happened to me, 2wd for me unless.....
Your dealer is clueless, there’s no problem doing what you did and they’re just trying to blame you because they don’t know any better or don’t know why it keeps happening. Auto is meant to be used any time without issue.

I suspect you’ll have the same problem again in a few months and this time they won’t be able to blame it on Auto 4WD.


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#38 ·
For some reason I read axle shaft seal, not output shaft seal. Front output shaft doesn't rotate if not in one of the 4WD modes.

However, their reason is still BS. Seals aren't load-bearing, the transfer-case is the same one as newer Jeep Grand Cherokees which are always in Auto 4WD mode by default with no 2WD option. If the transfer case output shaft/seal were wearing out within a few months due to being used on dry pavement then Jeeps would be having this done at the same interval.

If the seal is becoming damaged and needing to be replaced after a few months then I would lean towards a bad front driveshaft or some issue with the transfer case output shaft causing the driveshaft to "wobble" or similar and damage the seal over time.

There have been multiple complaints the same as yours, BTW. Ignore the thread title, some posts talk about a transmission seal but you'll see most are talking about the t-case output seal.

 
#39 ·
Funny thing is, when I bought my truck and drove it 800 plus miles home, and before I knew about bumping the 4WD knob with my knee getting in, I evidently bumped it with my knee and drove 800 miles home with it in Auto in the freeway. 2.5 years and 38K miles later, no problems. I do believe the posts linking to the tech papers on the transfer case, it does not hurt anything other than fuel economy to have it in Auto.

The system is awesome by the way, quick to respond and working great even in thick snow. I am not really sensitive enough to tell the difference between the Auto and 4 high settings when driving in snow. With the better AT3 tires on it, the truck is a beast in the snow.
 
#40 ·
Funny thing is, when I bought my truck and drove it 800 plus miles home, and before I knew about bumping the 4WD knob with my knee getting in, I evidently bumped it with my knee and drove 800 miles home with it in Auto in the freeway. 2.5 years and 38K miles later, no problems. I do believe the posts linking to the tech papers on the transfer case, it does not hurt anything other than fuel economy to have it in Auto.

The system is awesome by the way, quick to respond and working great even in thick snow. I am not really sensitive enough to tell the difference between the Auto and 4 high settings when driving in snow. With the better AT3 tires on it, the truck is a beast in the snow.
Did you bump it with the truck running or the key in the Run position? Remember, turning the knob to a 4WD mode with the key off won’t cause it to change modes when you start it.

If it was running and was shifted to Auto then yeah, no biggie. [emoji106]


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#41 ·
Who knows. Might have happened when I was driving it. Has happened a couple time since then and have read about it happening to other people on here too of course. Now I am completely sensitized to the location of the 4x4 knob and don't have this minor problem anymore ?
 
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