Ok, I needed new ujoints because of a squeek and squeal. I pulled the driveshaft and took the shaft to a mechanic to have the ujoints swaped out. Took the shaft back home and installed it took it on a test drive everything ok. The first time I took it up to 60mph I started to get a slight vibration. I did the exact thing to my last truck both are 99 f150 4x4. Never indexed either shafts (didn't know anything about this). Anyway when I installed the shaft I could see the old marks on the rear where the bolts lined up, so I thought I had it in right. After noticing the vibration I took the shaft off and rotated it 180 deg. and I still get the same vibration from 60-70mph. Any Ideas. P.S. the last truck I had I replaced the ujoints twice and never had a problem with vibration and did everything the same way this time.
My tires are not out of balance I just had them rotated and balanced and double checked for balance.
thanks-
scouty

 

Was one of the new u-joints "tight" after they were installed? They should move freely with no binding. Not flop around like a dead fish, but no hanging up at any place either.

The cups for the u-joint might be pressed in too tightly against the cross...this is what usually makes em bind. Either that or the guy might have sprung one of the yokes when he was removing/installing the u-joints.

I've never done the indexing thing on the transmission end when I've swapped u-joints either but I do mark with way it was on the diff yoke. Haven't had a problem doing it that way yet either.

 

Check your driveshaft at either end for any dimples or dents. The slightest dimple will make it vibrate.