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how does 4wd auto work

Discussion in 'GM Powertrain' started by newcheylover, Feb 1, 2013.

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  1. newcheylover

    newcheylover Member 1 Year

    I have a 2001 Chevy Silverado 1500 4x4 LS and would like to know how my auto 4wd works. I know how basic 4wd works an all but Never heard of this auto 4wd. I live in Michigan and some of the roads are dry but then others are ice. Do i need to disengage it when on dry road or is ok?
  2. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    You don't need to disengage it, but you should just keep it in 2Hi in dry conditions and rain and other mail weather. In ice or snow conditions keep it in auto. If deeper snow or off road like mud and bad trail just use 4Hi. You may never need 4Lo its for when your stuck and 4Hi isn't enough.
  3. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    As [MENTION=52248]Conlan Rose[/MENTION] suggests, you don't need to use 4AWD. The most economical selection is 2wd. The AWD selections does not send power to the front wheels until it is required (and it will do this automatically); however, it does engage an actuator in the front axles, causing them to turn (they run free in 2wd), resulting in slightly decreased MPG and an increase in front drive wear.
  4. newcheylover

    newcheylover Member 1 Year

    how does it engage and disengage?
  5. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    I believe your gen truck has a dial selector. Just turn it to the desired setting, except 4Lo to engage that you must be in neutral and traveling less than 3 mph. In my gen truck is is easy because it's just push button with light up indicators.
  6. newcheylover

    newcheylover Member 1 Year

    I have three buttons to choose from from the top auto 4wd then 4HI then 4LO. In my owners manual it says in order to shift into high or low 4wd You need to put it into neutral but not the auto. Im wondering about how it engages the front differential as its going. If I had to put it into neutral every time then it wouldn't really be automatic would it? Im wondering about the actual mechanics of it.
    Any ideas?
  7. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    You don't need to be in neutral to go front 2hi to 4hi just hit the button and it engages.
  8. MrShorty

    MrShorty Epic Member Staff Member 5+ Years 1000 Posts

    The 246 transfer case has a clutch pack inside. When you shift from 2H to 4A or 4H, it sends a pulse width modulated signal to the clutch pack to engage the clutch pack, which causes the front driveshaft to spin. When the front driveshaft speed matches the rear driveshaft speed (meaning that the front driveshaft is up to vehicle speed), it engages the center axle disconnect.

    If 4H is the selection, the clutch pack locks, and the front and rear are forced to spin at the same speed.

    If 4A is the selection, then it allows the clutch pack to disengage, and monitors front and rear driveshaft speed. When it detects slippage (rear driveshaft faster than front driveshaft) it sends its signal to the clutch pack to engage and send power to the front. Then it lets off the clutch pack to see if slippage is still there.
  9. newcheylover

    newcheylover Member 1 Year

    Sweet thanks for answering my question

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