Slight vibration when going 30-40mph

I have a 08 Tacoma 2wd prerunner and just had the seal that connects the driveline to the transmission replaced and now I get a faint vibration when I’m barely accelerating around 30-40mph but doesn’t happen went I’m accelerating fast... I do have a leak in my deff where the deff lock is. And I “had” a leak in my driver rear tire seal (I had fixed but questionable). Also sound like my bearing my be going out in that same tire. What could cause that vibration the bearing or it has something to do with the drive shaft(someone just touched)? I did lmbring it back to that shop and he tightened up the driveshaft and showed me where he put a mark to line up the shaft where it went. Any help would be appreciated..