check you rear pinion angle you are getting driveline vibration. Did you remove the angled factory perches?

 

The factory angled ones are still in there. Would an add a leaf throw it off a lot / would it only cause vibration at a set speed under acceleration? This is my first dealings with any type of lift and I’m learning as I go.

 

It shouldn't but that's what changed right? I put a 4" spring lift in mine which is 4 in the front and about 2.5 in the back and I don't have any vibration, maybe just a little bit.

Bronco's have a CV joint in the rear driveshaft so you want the shaft coming out of the transfer case and the shaft coming out of the pinion on the axle to be at the same angle.

How much lift do you think you added?

If your ujoints are tired, it may have been enough angle change to cause them to act up. Is there any slop in them at all? Jack the back up and take it out of gear and grab one end of the drive shaft on each side of the ujoint and twist around - any movement in and out or back and forth?

 

i had this same problem with my 82. Slight vibration between 30-40mph when accelerating... I'm not running a lift tho and I'm on 33x10.5s... But the problem was the rear drive shaft... The splines were shot... Rebuilt the rear shaft... And the front shaft and rt. front axle... slip joint and 2 U joints...
she feels great now...

 

Yeah I just had a buddy drive around with me to feel it and he thinks it’s the drive shaft also. I recently replaced all the u joints so that’s annoying. I’ll check for play in it tomorrow.

 

Also biggum the add a leafs are from super lift, it said 1-2 inches. It’s hard for me to tell what the lift is from stock height because my leaf springs were really worn out. I replaced the springs and put in the add a leaf at the same time, so it’s significantly taller than it was.