1995 Jeep Cherokee gear box

I had the gear box replaced on the front end; when I took the jeep out for the test drive before paying I noticed a deep vibration coming from the front end. The mechanic said that's natural for a jeep with high mileage; it isn't from anything he did he says. I told him drive it, he did and then said he didn't notice anything wrong, couldn't figure out what it woudl be. I told him check the drivers side motor mount. He calls back 30 min later and says."Guess what? I found out what the problem is. It's the drivers side motor mount but we didn't touch that part of you car.
my question.
don't you have to loosen the drivers side motor mount to get the gear box on/off?
rob