I have a 99 Expedition 4x4 with the 5.4l (recently remanufactured) and it has the A4wd, 4Hi, and 4Lo switch on the dash. When I am in A4wd and there is no wheel slippage everything is fine. However, once I shift into 4WD or there is some wheel slippage, and I turn, the front binds real bad. When I go straight everything is fine, but when I turn it binds and hops, almost like a full locker that is not allowing the wheels to turn at different rates. Any thoughts? Could my front gears be stuck together? I am not sure, it is fine when the 4WD is not engaged...

 

The binding is normal. When you are in A4wd the front and rear driveshafts are not locked together until the center axle disconnect (CAD) detects that the rear axle is spinning faster than the front, then the CAD acts like a limited slip differential and applies torque to the front axle. When you are in 4-hi or 4-lo the transfer case locks the front and rear axles together this causes the drivetrain to bind when you turn due to the wheels having to turn different speeds.

 

So on soft elements like sand or mud or snow where there is low traction it would be undetectable, but on asphalt where there is higher traction it would be exaggerated?

 

Yes

 

you got it!

it says right in your owners manual that the 4x4 should not be used on dry ground, that it can cause damage to the drive train, it should only be used when the tires CAN have slippage, eg. snow, mud, sand, ice, possibly rain.

in the old days before we had the electronic 4x4 , you sometimes had to put the truck in reverse and backup to "unbind" the front and rear axles so u could take it out of 4x4.