Nissan Repair: Engine Noise, nissan altima, cv boots

Question
I have a 1993 Nissan Altima SE, manual with 224K miles which I have had since 44K.  I had both drive shafts replaced because the CV boots were torn and clicking, shortly afterwards my driveshaft was jammed in my transmission becasue of the wrong part.  The dealer had to take the tranny apart to get it out and fortunatley they said it did not damage anything in the tranny.  Ever since they did this my car engine seems to be rough especially when I initially start it up.  I especially hear the rough noise when I go over dips in the road particualary when the car go downs in the dip and without pressing on the accelorator as if the noise reacts to the imperfections in the road.  Almost as if the engine is not stable.  It almost sounds like they didn't put everything back together and 2 of the 3 motor mounts I can see appear to be compressed.  Any ideas?

Answer
It sounds like you have a loose or broken motor mount.  Perhaps, the driveshaft on the passenger side since it is longer is bumping into something when you hit bumps.  You can look under the car and see if the driveshaft has shiny spots on it and that is the shaft that goes through the cover that it could tap against.  I have had this happen before where the inner fenderwell was not put back on properly.  ALso, to check for broken or loose motor mounts all you need is a person looking at the engine while you set the parking brake and then put the car in forward and let the clutch out a bit to load the engine and see how far the engine moves and do the same thing in reverse.  Be sure the parking brake is set tight and make sure no one is in front of or behind the car.  All you are doing here is just start to load the engine in both directions looking for excessive movement.  If you have a motor mount that is broken or loose you will see it right away.