4th gear 2800--3K rpms
My bad, it continued vibrating.... But what's really baffling is why doesn't do it in any other gear but 4th..
Thanks.
No worries. Get the car up in the air on both ends, grab a long thick screw driver or awl type prybar, some gloves and a flashlight. Leave the transmission in gear and use the prybar to try and move the u-joints back and forth while looking closely at them for any sign of sloppiness.
Also, see how much play there is between the front driveshaft yoke by grabbing it and moving it side to side. Can you see any movement? How much? Is it more than a stack of 3 or 4 playing cards?
If that all checks out, pull the driveshaft out, be ready to catch some gear oil out of the trans, and rotate it 180 degrees and reinstall.
Are all your tires and rims the same size? Was the car sitting on them for more than a few months causing them to flat spot? Take them down to a tire shop and have them balanced again. Ask them to let you watch each tire get balanced so you can see any runout will they are spinning.
While the tires are off, check to see if the face of the axle flanges have any excessive runout.
