when i back up or even park on a hill and put it in N when ever it goes backwords it shakes like hell and if you want the tires it goes 4 inchs then like stops almost and does that for as long as you go backwords thouth maybe u joints so i changed the back 3 didt do anything could really use some help thanks guys have a good christmas D.J.

Might check rear parking brake shoes.

does the truck pull to left or right, when braking? if not then, i would also start to look at the parking brake's to see if they are siezed up. i would also check the caliper's to see if one of them is frozen up. i had a problem similar to that, the truck would buck when leaving red lights and it turned out to be a frozen caliper. let us know what you find out.-Sean