4x4 help

[Agamarne]

I recently bought a 4x4 Silverado 1500 2015 Rally 2 Edition and it's my first truck with 4x4. I'm used to the AWD Subaru STI and have left the 4wd selector in Auto because the salesman never told me about the knob. Now what conditions should i have the truck in 2 wheel drive and in what conditions should i put it in auto 4x4 4x4 high or 4x4 low, and is auto 4x4 not good to run the truck in unless there is snow, etc? i'm a little confused as i thought auto would decide whether or not 4x4 is needed, but after driving it for not even a few hours i started to hear a very high pitch chirp and the mechanic there said they couldn't duplicate the noise or hear it, got my truck back it was in 2 wheel drive and they did tell me not to have it in auto mode 24/7. Any help on the differences would be great as well as what that high pitch chirp/squeal could be, it wasn't constant and only happened when shifting to drive reverse or park or releasing the gas or break or starting off from a stop.

[PrairieGM]

Hope this helps, and anyone else please chime with corrections and/or more info. 

 

2WD is the main day to day mode that should be used on good traction surfaces. Best fuel economy and least wear on components. 

 

4 Auto is more for inconsistent/patchy conditions, such as patchy ice on roads. Transfer case will automatically switch between 2WD and 4HI based on wheel slip. Personally, I never really used this mode on my old pickup. 

 

4 High is for rougher conditions, deep snow, etc. but allows you to still run at higher speeds. Transfer case will be locked in 4HI. I use this the majority of the time, especially during winter but still is useful in off road settings. Should not be used with high traction as turning will cause the system to bind and eventually prematurely fail. 

 

4 Low is low range on the transfer case. Transfer case will be locked in 4LO, must be basically stopped and transmission in neutral to shift into it. Meant for really rugged conditions and/or where low speed control is needed. Increased torque but limited top end speed. People use it for off-road situations, such as rock climbing, I mainly used it in fields while dragging trailers. Again, should not be used with high traction. 

Edited January 31, 2020 by PrairieGM
Add a few more details that I forgot earlier.

[swathdiver]

On 1/30/2020 at 6:12 AM, Agamarne said:

I recently bought a 4x4 Silverado 1500 2015 Rally 2 Edition and it's my first truck with 4x4. I'm used to the AWD Subaru STI and have left the 4wd selector in Auto because the salesman never told me about the knob. Now what conditions should i have the truck in 2 wheel drive and in what conditions should i put it in auto 4x4 4x4 high or 4x4 low, and is auto 4x4 not good to run the truck in unless there is snow, etc? i'm a little confused as i thought auto would decide whether or not 4x4 is needed, but after driving it for not even a few hours i started to hear a very high pitch chirp and the mechanic there said they couldn't duplicate the noise or hear it, got my truck back it was in 2 wheel drive and they did tell me not to have it in auto mode 24/7. Any help on the differences would be great as well as what that high pitch chirp/squeal could be, it wasn't constant and only happened when shifting to drive reverse or park or releasing the gas or break or starting off from a stop.

4AUTO engages the front propeller shaft so it is turning, ready to send power to the front wheels the nanosecond the computer tells it to.  There is an actuator on the right axle tube that will engage the axles at this point.  This mode results in slightly reduced fuel consumption.

 

We use it in torrential rains and up north you can use it if you suspect ice or patches of snow, etc.  4HI is for off-road use, soft sand, dirt roads, mud, etc.  If you have the TC set for 4HI on a paved road and go to turn, you will hear the driveline protest, such as while turning in a parking lot.  Keep your fluids clean, change them every 50K miles and the driveline should last you a long time.  What year truck?

 

[Colossus]

Just know that being in 4Auto it won't respond quite as quickly as it would locked in with 4WD.  "Transferring power from the wheels that slip to the wheels that grip" as the old Subaru tagline goes.. and as with other AWD vehicles.. it can take a second or more for the computer to figure out which wheels to transfer to.  But when you are locked in like it is when in 4WD, instant power to the left front and right rear tires.  (so why do they call it 4WD when it's really only 2WD eh?  ha ha)  So on very snowy and icy surfaces I will keep it in 4WD but occasional snow/loose traction situations I would keep it in auto.  But on dry pavement 2WD.

[Dunn]

I still haven't used mine at all, we get heavy rain sometimes but to be honest this truck is a dream in rain, never drove a vehicle so planted and controlled in heavy rain, and this was all in 2wd....I do have stock Michelin street tires tho, they cut thru water superbly

[swathdiver]

2 hours ago, Dunn said:

I still haven't used mine at all, we get heavy rain sometimes but to be honest this truck is a dream in rain, never drove a vehicle so planted and controlled in heavy rain, and this was all in 2wd....I do have stock Michelin street tires tho, they cut thru water superbly

They sure are, let me suggest that you get in the habit of exercising the transfer case, running it through all modes once a month or so.