Knocking in engine compartment

toyota
4runner

#1

Had the transfercase seal replaced on 99 4runner 4wd on dealership recommendation. Approx 2weeks later attempted to shift into 4wd high by pressing button on side of shifter, but would not engage after driving 5 miles. Stopped car to try other 4wd options and finally got to go into gear, but after going into gear, started hearing knocking sound in the front of the truck when in a gear. Sound does go away when in park or neutral. Dealership says that I have bad main bearings.



The sound is easily heard neither I nor my wife heard it prior to this last repair.



Could the process of repairing the seal have caused this problem?