ok i have a 74 f250 4x4 aka (highboy) 4 speed. everytime i get a little foot heavy and spin tires the rear end bounces like a sob. 2,3,4th gear. they all do it and its got a true trac, posi rear end it did it with 35s 33s and is doing it now with 31's. so what do i need to do to eliminate this. stock hieght. and if u recomend trac bars. can you tell me the pros and cons of using them. truck does leave the road anymore.

 

The bouncing is the rear axle twisting, you have 4" blocks between the leaf pack and the axle creating a lot of leverage,

When you jump on the gas the axle rotates and causes the springs to twist, when the spring has twisted to its max that energy is then released causing the tire to jump up and spin free for a sec,

Then the tire hits the ground and stops rotating and the whole process starts over again, hence the bouncing,

Perhaps you should consider not doing burnouts any more, it's a 4x4 pickup truck not a '69 Mustang.

 

Do as many burnouts as you want just add a traction bar first! I would suggest a 1 ton rear axle too if ya really wanna step on it with bigger tires with bigger u joints. You only need 1 bar as well not 2.

Here's the one I made

https://www.ford-trucks.com/forums/975221-trac-bar.html

 

Its caused by axle wrap. Axle wrap is common on any leaf sprung truck thats mounted spring over axle... its made worse by soft springs and bad shocks. Of course adding stiffer springs made your ride worse, so its not a good solution. It happens because the axle is trying to rotate and the pinion is trying to point down, and as it flexes the spring it binds and releases, and snaps back up, only to repeat. if you don't fix it you will break stuff, usually U joints but sometimes yokes, driveshafts, axles, or even pinions. So what you need is something that stops the axle from trying to twist the spring in that direction. a traction bar is effectively a radius arm that allows the axle to still move up and down vertically (actually elliptically, but any traction bar of decent length will hopefully have negligible fore to aft movement through its travel) but not forward and backward, which prevents the spring from binding and thus prevents the axle wrap. Because a leaf spring cycles up and down vertically, and traction bars do not truly cycle vertically, the traction bar will usually make the truck ride stiffer, since the leaf spring has to conform to the elliptical cycle of the traction bar. On long travel applications the traction bar effectively limits the travel of the leaf spring.

this style traction bar has gained popularity, since it can allow more articulation: Superlift Traction Bar Kit

If you do use a traditional ladder bar, its generally thought the longer the bar the closer it will cycle to vertical and therefore the better. The longer the bar, the more it may potentially eat up your ground clearance.

Here are some cool unitized blocks, these particular ones are made for the superduty, but you get the idea.

Fabricated Unitized Floating Traction Block - Precision Metal Fab

 

Never seen that superluft traction bar/ spring setup before. Wonder if it works?

Just to throw another idea out there I've thought about a bam bar for my other 79 f250 pickup

Read here

BamBar - Ultimate Anti-Wrap Solution - Jeepaholics Anonymous