Looking for some help fixing my 93 YJ?

1993 YJ, 5sp 4 cyl, when accelerating, vibration is felt in 1st 2nd and 3rd gears. Not so much in 4th or 5th. 2nd is definitely the worst. Vibration is worst under load, and disappears when the clutch is pushed in. All universals are good, drive shaft straight, tires balanced. Any ideas?