I recently replaced the front struts and springs on my Grand Am. I had the wheels aligned immediately afterwards. When I drive the car the front end has a very noticable "thumping" that sounds like it is coming from the suspension. I have put the car on jack stands and tried to shake the strut assembly to replicate the noise, but have had no luck. I also checked the tightness on all the nuts and bolts. Everything looks in good shape and nothing appears loose. please help me on this.