Vibration Question

[onebig76k5]

I'm getting an oscillating vibration thats sets in around 50mph, with a period of about 1s. It fades around 60mph. Vibration was before these items so you can discount them as the suspects (lengenthend and balanced drive shafts, LI/LO hubs, 35/12.5 tires BFG Mud, rebuilt rear end with eaton posi, 4.56 gears, new axles, bearing etc, new tranny, new 383). I asked the drive shaft people about angle induced vibration and was informed that drive line angle vibration would be prevelent from 10mph to infinity, so they didn't think I had and issue with angle. The vibration will smooth instantly when you decelerate. Any comments? Thanks.

 

[Confedneck79K30]

lengthened and balanced dshafts doesnt mean you didnt have a ujoint fail, could be that, could be pinion angle, they set in wherever your truck lets you feel them, they could be cancelled out by millions of things... my advice is...
start the truck and let it idle, loosen slightly all the exhaust bolts and clamps that hold the exhaust together, wiggle them by hand and retighten, this will eliminate exhaust vibrations... then check driveline angles, pinion to output, and inspect your ujoints for ANY slop or broken caps... also you can neutralize your engine and trans mounts along the same lines as the exhaust

 

[readymix]

I would guess a u-joint