An angle finder. Check the angle of the pinion/yoke and angle of output of the transmission. Should be the same or within 1*

Here is a pretty good link to explain.
http://www.drivetrain.com/driveline_angle_problem.html

 

Thanks this is alot of help in finding the problem. I think the truck had a leaf spring taken out at on time. This was done when I got the truck by someone else for looks. It never done this when I had factory gears and unit, I put a eaton possi and 410 gears in for quicker times with a little 100 shot. It only gives me problems when I get about 75+ and levels off when I reach back to this speed. I thought it was something I could live with until I lost a drive shaft at 110 mph. I was lucky that the truck did not flip over. This little problem got big when I paid 489.00 for a drive shaft and yolk. I wonder if the front is lowered a little I could get the levels I'm looking for?

 

Lowering the front wouldn't effect the driveline angle. The front drops but the transmission to rear pinion angle isn't affected like when you move the rear end up or down.

I understand the concern with vibration. I am starting to feel some vibrations from time to time that I hadn't noticed before. I am goning to start going through the process of checking everything out and getting the driveshaft balanced.

 

when you find your problem advise! I would like to know what it was! I have a new drive shaft and will check it too, but the old one did the same thing so It could be the angle of my pinion.

 

I see your time on your truck and you must have a killer 60 foot time. I get 100 or 100+ but and stay in the 13s and my 60 foot time sucks

 

 

High 1.7 to mid 1.8 60' times. Hoping to improve these with the new suspension and gears.

I'd be willing to bet your vibration and mine are due to bad pinion angles. I got mine after the rear gear change. Only have a vibration under hard acceleration. The 4.10's putting more torque to the rear, wrapping the axle harder, to the point of a bad pinion angle and the vibration. I am fairly confident a set of 2 or 4* shims will fix mine. In my case I will probably need to increase the pinion angle by adding the shims fat end toward the front of truck.

 

your killing me!

 

Try a 1* shim first. Changing the angles in 2* increments is not recommended on a stock suspension. The 1* shim with the fat side to front should fix your axle wrap issues under hard accelerations.
My truck is about to be sent to the scap yard soon!! Can't get the vibrations out. Now all I'm left with is going to a 1-piece aluminum DS or back to stock!!!
I hate my truck now..........

Jim