Using 4x4

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Jeff Dodson, Sep 29, 2013.

  1. Jeff Dodson

    Jeff Dodson Member 1 Year

    Ok second post, trying to get that ad off..

    anyway. What is the proper uses procedures for the electronic 4x4 on this truck. 99 GMC Z71 new style... I don't have the owners manual yet, the lady is trying to remember to bring it to work for me but memory is as bad as mine

    in other does it have to be stopped in park, in neutral , 4x4 LOW,,, and then back to 2WD mode..... Do I have to back up for so far to release any locking hubs.... ???? Sorry, I know nothing about this thing and as I said! I have no owners manual yet...

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    Nobody knows how to work the 4x4 ????
  2. j cat

    j cat Epic Member 5+ Years 1000 Posts

    so this 1999 GMC truck has locking hubs ?

    If this is an OEM 1999 GM truck you simply push the on dash buttons to command the drivetrain to enter 2/4wd/auto ....

    this 4WD is not full time 4WD. you must never operate in ANY 4WD selection on solid dry pavement at any time. the other warning with this is make sure you rotate the tires often and make sure all tires are of the same size and wear. this will reduce the wear of the drive train components.

    these vehicles require frequent fluid replacing especially if used to do typical truck work. fluid replacement of all the drivetrain components is 30-40,000 miles.

    due to changes made in the fluid requirements make sure you check that the proper fluids are used. DEXRON III WAS the correct fluid NOW it is DEXRON VI.
  3. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Perhaps this will answer your question.

    -I'm sure you are aware, the 2WD is the "normal" mode to be in while driving on dry hard surfaces.

    -The AUTO4WD is an attempt to provide full time 4WD in these trucks. In this mode, the drive-train is ready for a 4x4 need. When the controller senses rear wheel spin, the transfer case clutch packs operate sending power to the front wheels. You can stay in this mode on hard dry surfaces; however, some parts of the 4x4 driveline are operated, so your gas mileage may suffer.

    -4WD HIGH is the "normal" 4x4 mode. This is the position to select when driving in conditions that require front and rear traction (off-road, ice and snow, etc) You can switch into and out of, 4x4 HIGH at any road speed.

    -4WD LOW, low speed 4x4 requirements. You must be stopped, or very near stopped, and in neutral (transmission), to switch into, or out of, 4x4 LOW.

    I'm not sure about your t-case, mine also has a neutral position.
  4. Jeff Dodson

    Jeff Dodson Member 1 Year

    thanks Ray, that was close and much needed info on the AUTO 4WD... Question is, what about the HUBS, they are NOT manual hubs... Just asking, do I need to back up to release the hubs, like the older auto locking hubs ???
  5. j cat

    j cat Epic Member 5+ Years 1000 Posts

    I would not operate the vehicle in any 4WD including auto on dry solid pavement . this causes drive train wear . THIS IS in the OEM operating manual. I use the auto 4WD when in snow / ice conditions works quickly and there is no indication of actuation. you will feel a slight vibration when in this mode due to the front axles . you will loose MPG in this mode.

    never operate the vehicle with tires of different wear. rotate often .

    this 4WD is designed to engage when moving in the high mode. when selecting the low 4WD this is only used when stopped or when moving very slowly like 1 MPH ..... there are no hubs with locks. this is all done by motors and monitored by a computer. when these fail the service 4WD light will show.
  6. Conlan Rose

    Conlan Rose Epic Member 5+ Years 1000 Posts

    To answer your question, no the hubs will lock and unlock as needed without user interference. The 4x4 system on all GM trucks 1988 and newer have auto locking hubs. This was done so 4x4 could be activated and deactivated at any speed without worry. You only need to stop for 4wd LOW because the transfer case needs to switch gears which it can't do while in motion.
  7. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    I agree with you Conlan, My owners manual for my 1995 says that it may be necessary to back up 30ft to unlock automatic front hubs. I don't know why considering that it is basically the same front end as my 2005. I wish I could find that manual now. It could have been a typo just like the fuel filter for the 2006 trucks
    Last edited: Oct 1, 2013
  8. Jeff Dodson

    Jeff Dodson Member 1 Year

    Thanks yall are great

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