jeeeep
Hooked
I thought it was the parallel relationship between the front and rear axle, the side-to-side movement won't matter if the axles are parallel.That's how the rear axle center is compared to your front axle center. But on a Jeep it's tricky because of the way the track bar causes the thrust angle to change over every single bump as the axle moves. If each axle is centered perfectly, they still move as soon as you start driving so it's pretty useless to measure it on a Jeep.
But, if the thrust angle is off it can have an impact on whether the vehicle feels like it's going straight or off to one side.