Gmt 800 Auto 4wd Vs 2wd?

[uchi]

wondering about the auto feature. i see my truck is always in this mode. i figure its gms way of having a traction control of some sort. but im wondering if i keep it in 2wd will it get better gas milage? also when in auto mode if i do loose traction does it engage the transfer case and lock the hubs or is the case already engaged and then the hubs just lock?

[Matt_]

wondering about the auto feature. i see my truck is always in this mode. i figure its gms way of having a traction control of some sort. but im wondering if i keep it in 2wd will it get better gas milage? also when in auto mode if i do loose traction does it engage the transfer case and lock the hubs or is the case already engaged and then the hubs just lock?

 

If you're not in an area that may cause you to lose traction, it's best just to be in 2wd.

 

when in auto, the front diff actuator engages for gears so your front diff and driveshaft will turn. The t-case motor moves into a "ready" state (for some trucks, this causes a binding feeling when making sharp turns at slow speeds) and fully engages the front axle when wheel slippage is sensed.

[uchi]

thanks for the info, that could explain the binding i was feeling pulling out of a parking spot a couple times tonite. is there any way through the dic to select the truck to start in 2wd mode all the time rather than auto?

[Matt_]

Nope... just leave it in 2wd. If you think you're going to need auto mode, you can press the button any time on the fly- you dont have to be pulled over or anything.

[KMGZ400]

thanks for the info, that could explain the binding i was feeling pulling out of a parking spot a couple times tonite. is there any way through the dic to select the truck to start in 2wd mode all the time rather than auto?

 

 

sop when you start your truck, its always in 4wd Auto? if so, i think thats a problem

[Matt_]

oh yeah, i didn't read it like that.

 

If your truck turns on and is already in auto then you have an issue. Default is 2wd. Sorry i misread that previous post

[Snow White]

is your dial/knob set to auto or 2wd?

[uchi]

oh good go know thanks guys. its going back today for a power seat issue to the dealer so ill mention that to them.

 

mine doesnt have a knob its 4 buttons. 4wd auto being at the top, then 2wd, 4hi and 4 lo. i figured being in auto mode all the time would likely work the t case and eventually cause something to take a crap on it. ill add it to my little list that ive started. gotta milk that expensive aftermarket gm warranty all i can. lol.

 

thanks for the help fellas.

[jdewolfe]

I'm pretty sure that it doesn't default to 2HI. I believe when you restart it will be in the same mode as when you shut it off. So if you shut it off in 4HI, it will be in 4HI when you restart. If you shut it off in 2HI, it will restart in 2HI. So yeah, just put it in 2HI and try shutting it off and turning it back on. Should stay there. If not, definitely mention it when you go to the dealer.

 

Jeff

[Matt_]

For some reason I thought that if you're in auto mode and shut the truck off it would go back to 2wd upon startup and if you were in 4hi or 4low then it would stay in 4wd.

 

Could be wrong though. I'd definitely put it in 2wd and see what it does when you restart it.

[KMGZ400]

ohh... i forgot that it does that in what ever you put it in, Auto, 2, 4hi 4lo, it will always stay whatever you leave it in after restarting

[uchi]

dealer scanned it and updated some codes as they put it. but according to the tranny tech at the gm dealer its perfectly normal for it to start in auto 4wd mode. i have however put it into 2wd mode and after shutting off and restarting the truck it goes back into auto mode. seems to default there for some reason. maybe ill try holding the 2wd button and listen for a beep or something. im not a fan of it being in auto mode so ill just be sure to remember to use the 2wd button. although ive got 80 000 km worth of warranty on this thing so if something starts to fail ill be good to go, but i bet it wont happen till 80 001 km from now, lol.

 

thanks for the help guys

[Matt_]

dealer scanned it and updated some codes as they put it. but according to the tranny tech at the gm dealer its perfectly normal for it to start in auto 4wd mode. i have however put it into 2wd mode and after shutting off and restarting the truck it goes back into auto mode. seems to default there for some reason. maybe ill try holding the 2wd button and listen for a beep or something. im not a fan of it being in auto mode so ill just be sure to remember to use the 2wd button. although ive got 80 000 km worth of warranty on this thing so if something starts to fail ill be good to go, but i bet it wont happen till 80 001 km from now, lol.

 

thanks for the help guys

 

That IS a problem

[dlstewart01]

I don't have a 4X4 but I remember when I worked in the dealership in 04 and 05 they did not do that. If you had it in 2 wheel drive, it stayed there till you pushed another button.

[c4cruiser]

dealer scanned it and updated some codes as they put it. but according to the tranny tech at the gm dealer its perfectly normal for it to start in auto 4wd mode. i have however put it into 2wd mode and after shutting off and restarting the truck it goes back into auto mode. seems to default there for some reason. maybe ill try holding the 2wd button and listen for a beep or something. im not a fan of it being in auto mode so ill just be sure to remember to use the 2wd button. although ive got 80 000 km worth of warranty on this thing so if something starts to fail ill be good to go, but i bet it wont happen till 80 001 km from now, lol.

 

thanks for the help guys

 

Got to disagree with the "tranny tech", it's not "perfectly normal". My 99 Z71 with auto 4WD never did that. While I can't recall leaving it in Auto 4WD when I shut the engine off, I can safely say that upon engine startup, the truck was in 2WD. I had to select a 4WD mode by using the buttons. You could have a bad solenoid or even a bad switch.