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4x4 old style

Discussion in 'Ram Trucks' started by DAZ982500, Sep 30, 2008.

  1. DAZ982500

    DAZ982500 Senior Member
    Messages: 142

    On a Dodge 77 the 4x4 is not lock out hubs but a contol lever on the floor a bit off center.The question I have is what is the differnce between HI loc,vs HI and what is neutral for.It appearsd as though the truck has to be in Hi loc for driving purposes.Is the truck in four wheel drive all the time,or is a 20/80 drive front to back.When do you change from the HI to Low when in neutral (transmission).Is anyone familiar with this 4x4 system.I purchased a Dodge 77 11/4 ton power wagon was former fire appratus.I am not familiar with this system.I also have aolf Fisher speedcaster plow,with hydro control system that I am going to have installed on truck.The truck has 20k miles which I got for 3k.THANKS DAVE
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Very familiar with these old war horses.

    The NP203 T-case is full time 4WD and has no "2WD" mode, only Hi, Lo, and of course the Loc positions. In Hi, everything works normally just like any FULLTIME 4WD vehicle, but there is a differential inside the T-case that acts constantly, putting power to the front and rear, but at the same time allowing either axle to spin independently one one another as necessary...allowing turning without any drive train binding under normal driving conditions such as dry pavement. Lo works exactly the same way, albeit with a 2:1 gear reduction for extra torque. When you place it in a "Loc" position this eliminates the differential action in the T-case and makes it just like a part time 4WD with it engaged in 4WD, ie you now have both axle locked together turning at the same 50/50 torque split, thus turning at the same speed no matter what. This mode is used only in low traction situations like snow, mud, sand, ice, etc....never to be used on firm ground or good traction situations.

    You can shift into or out of a Loc position at any speed as long as the wheels aren't spinning...but you want to stop or be moving very slow (1 or 2 MPH) with the transmission in neutral to shift from low to high or vise versa.