Vibration issues

I didnt rise the front I only went from 14inch to 15inch wheels. I didnt adjust suspension. I kept the same tire size. I changed leaf's because the old ones were old and sagged. I didn't have the issue when I changed the leaf's. This issue began when I I swapped in the different gear set.
The shop had the old shaft and used the old front and rear yoke on the new shaft when they made it.
I was at my school when I put the gears together I had help from my instructor still not saying I didn't do something wrong. That's why I went back to the gears I had in before I had the issue.
I still had the 14s on the front when the vibration began
I ran the car with out the drive shaft to see if I could feel I vibration in the transmission I did not feel any weird vibrations. I am planning on removing the rear tail housing and checking the shaft and replacing the rear bushing to. so no I have not looked through the transmission yet. Have not had time to do so. Still have not ran the car on stands to find any other causes yet.