tranny?

[orviskid]

2012 sierra 4x4. when do you use the auto button??? i'm assuming thats like AWD. why would you need AWD when you have 4WD??

[kstruckcountry]

It's generally good to use it in icy conditions. Basically the transfer case and front axle aren't coupled, but the driveshaft actuator is in. As soon as the truck detects slip it sends power to the front so you have 4 wheel drive.

[elite0259]

Its Auto 4WD... Not All Wheel Drive. It prepares the 4WD system but doesn't actually lock the front/rear axles together until wheel slippage is detected.

[vkjohnson]

Just like above. It's great on patchy snow or slick areas.. Even during rain I can get a little rear wheal slip under normal acceleration, taking off from a red light. Auto stops the slip. You shouldn't have it in auto all the time though, hurts the MPG some.

[PS4570]

I too confused auto 4WD with AWD in my 2003 and ended up needing my transfer case rebuilt after a couple of years - I don't remember the mileage off hand. The service writer at the dealership told me that auto 4WD should only be used in really slick conditions like snow and that I had "burned up the clutches" by using it too much. I pointed out that the owner's manual didn't say anything like that. GM ended up doing a full repair under warranty.

 

I don't know how that info translates into a 2012 model, but your question hit a cord with me. (Ten years later and I'm still driving my '03.)

[kstruckcountry]

I should add that while you can use it at highway speeds, it will wear faster and decrease mpg some as stated above. Most people use it around town or going slower than usual in bad conditions.

[orviskid]

so not on the highway? that would be the only place i'd use it because i'd have a nasty ride home 28 miles on the highway.

[PS4570]

When the conditions warrant it, I use Auto 4WD, including at highway speeds. I just no longer use it most of the time as I did prior to needing a rebuild (e.g., I now seldom engage Auto 4WD in the rain and floor it away from a green light ).

Seems to work for me - it's probably been close to 100k miles since I needed the internals rebuilt - assuming the cause was really due to overusing Auto 4WD.

[kstruckcountry]

Using it on the highway won't hurt anything, but unless you think you'll need it, there's no sense leaving it on all the time. But in sketchy conditions it's great to have on.

[Shaners]

When conditions are bad use 4WD. When they are just questionable use AUTO. In Auto you won't bind the driveline going around sharp turns in town if they aren't super slippery.