I have a 2002 F250 Crew Cab short box.  I installed a 3" lift on it (springs front, block in back), and now at take-off and again at about 80mph I get a driveline vibration that it never had before.

Can anyone tell me what the cause is, and how to fix it?

Thanks,

KEN

maybe the pinion angle is screwed up at the rear axel?  

Thought about that, and went to my local alignment shop to have them look at it as they did my alignment.  They checked the angle and it appeared fine.  They shimmed the carrier bearing (to lower it) about 1/2" and it shifted the vibration from about 79mph to about 83mph.

I have seen some lift kits offer a shim kit for the carrier bearing, but only call for it on 4" or taller lifts.

I am thinking I need to drop the carrier bearing about 1-2" in order to solve the problem now.

If anyone else has any comments or thoughts, please let me know.

Thanks to all,  KEN

I have seen some things like this and it could possibly be either a driveshaft that is too short or an unbalanced drive shaft, granted it might not be either but both of them are possibilities  

I agree with the driveshaft idea, its a good possiblity on a truck that new.   I'm not quite sure what style of yokes are on your driveshaft but here is another fix that may work.  Can you take it off, rotate it 90 degrees and reinstall it?  I know you probably tried it already but sometimes you overlook the obvious. 

You could also take it to a driveline shop and have them balance the driveshaft.  It is easy for them and doesn't cost much. 

If all else fails I would check out the front axle.  I have seen some vibrations that only show up at certain speeds from the ball joints being worn slightly.

Hope you fix it or you'll have to learn to keep that lead foot of the accelerator.

Sounds like you have a nice truck. As for the drive train vibration, well I assume that with a 3 inch lift you installed larger tires. You say that you had the pinion angles checked, and they were fine. Did you have the larger tires ballanced when they were installed? Not all tire shops can ballance large tires. Also, go back threw the steps of installing the lift and make sure that all the bolts are tight. Some may have rattled loose at 80 mph. Good luck.   

lticepick

try installing tyour factory tires and rims and taking it for a drive.  

Double check all of your U joints and slip joints in the driveshaft.  If the slip joints don't have enough spline engagement it can cause a slight vibration. Although it shouldn't be a factor with just a 3" lift. I hope that helps.