Knocking/Vibrating Sound Under Front of car

I have an 2001 Automatic Honda Civic LX 4-Dr Sedan.



For almost a year now, we have had what I can only describe as a “knocking/vibrating” sound coming from under the front of our car. Nobody can seem to figure out what it is.



The sound comes when traveling at speeds less than 50 mph. It sounds like something is shaking, or loose. When the sound comes and I take my foot off the gas, the sound goes away.



The mechanic has basically replaced the entire suspension of the car and that has still not solved the problem. We also had to have our transmission rebuilt because of a different problem. Could the two things be related? Should I take the car back to the mechanic who rebuild my transmission?