Sponsored Links (Register now to hide all advertisements)
A good guess i that the replacement transmission is slightly out of alignment with the clutch disk and pressure plate. If it is slight, it usually will set up a periodic vibration of the type you describe. The usual fix is to put the rear wheels off the ground with good jack stands, then slightly loosen all the transmission to clutch housing bolts. Run the engine and drive train in third gear as a helper exercises the clutch pedal, then tighten a couple of bolts on each side. Shut down the engine and tighten the rest of the bolts. Lying under a running car requires precautions, of course, so be sure the vehicle is secure. Genuine Ford u-joints are tough, and can outlast the vehicle. Repros, not so much. As you didn't have the vibration before the change, it is unlikely the u-joint is bad, unless you have neglected greasing the u-joint housing.