Like he said, traction bar will help.
The problem is that the axle twists in the leaf springs and untwists back and forth and this is called axle wrap and can lead to the wheels hopping up and down.
URD has a very nice traction bar to prevent this. Right now we have it available for the Tacoma SRunner street truck. We will soon have it for the new XRunner and the rest of the 2x4 line of trucks. We will also have them for sale for 4x4 applications.
As you can see it is a unique design and uses a single bar that runs along the propeller shaft.
It uses a very stout bracket that bolts to the diff assembly that is presicion cut on a LASER.
The front mount attaches to the frame cross member that supports the propeller shaft carrier bearing. The street truck version uses a unrathane bushing. The off road versions will use an articulated joint with a high quality heim joint.
The SRunner guys are eating these things up!!!