I just bought an old thrasher dodge ram, 1996. It's a 4x4. I was out picking up some firewood, and got stuck in the ice. The guys at the firewood place said that only two of my wheels were spinning - the front left, and the rear right. I later talked to my mechanic, and he said that that was normal. Can someone explain this to me? I thought 4x4 meant that all four wheels were powered.

 

You have open differentials in both axles or possibly a limited slip in the rear which works like an open diff when the clutches are worn out. Open differentials always send the same amount of torque to both wheels, but since energy takes the path of least resistance that torque is determined by whatever wheel has the least amount of traction. If you have one wheel on ice and the other on solid pavement just the wheel on ice will spin since it takes very little torque to spin that wheel, the wheel on pavement will be getting the same amount of torque but won't be getting enough to turn that wheel. Limited slip differentials work by using clutches or gears depending on the type to transfer torque to the wheel with greater traction. Lockers make both wheels on the axle turn at the same speed regardless of the traction. If you want "true" 4x4 where all wheels turn at the same speed you have to install lockers in the front and rear axles.

 

^^ What he said.

I am not a fan of lockers in the front axle though.... maybe a selectable locker? So you can get the best of both worlds.

 

^^^what he said

Marisa Tomei explains here (not kidding):

 

Haha, love that movie!
If all four wheels turned the same speed, you'd only drive straight ahead. Be thankful your old "thrasher" actually has operating 4x4.