97 Dakota rear end pivots up & down

The rear end moves or shimmys up and down on fast take off or hauling a load(trailer). i was told it could possibly be something with the leaf springs needing tightening... don't know whats up? did have all the u- joints checked and they were fine, also the carrier bearing was changed. Help me please!

if you're going to be hauling or pulling a trailer, you need to get beefier leaf springs. I have 3/4 ton leaf springs on my 95 Dakota V6 and air shocks and I have no problem with hauling or towing.