Rear wheel hop

[miller502]

At 40mph, my rear end starts to hop. The tires are balanced rims are not bent and i swapped the rear to the front and same thing happens. I am running 35x12.50x18 tires and rims. If I go past 40.....it stops. If I am under 40.....it does not hop. Could it be the rear shocks ?

[kafleming19]

I had the same thing going on with my 87 4runner and it turned out to be the u-joints on my drive shaft.