OK, I am having this problem only when the outside temperature drops below about 45 degrees or so, and the car is completely cold (not driven for at least a few hours)

On startup it has a thud-thud-thud sounds you can audibly hear and feel in the pedals somewhat..when I go under the car or in the engine compartment it sounds like nothing, you can really only hear it from inside the car. After the engine warms up a bit it goes away. HOWEVER I do notice if put into gear and some pressure is let off on the clutch the noise goes away with just a tad of pressure in 1st gear, in a higher gear it takes a lot of letting up on the clutch to make the noise go away, almost stalling the car. (holding the car in place wit ebrake) when using REVERSE to do the same thing..the noise is a little louder. Driving on bumps seems to make the sound come and go as bumps are driven over. I do have a replaced trans and clutch from nissan and also have the timing chains and all that tsb replaced. so I doubt it's any of that. The car was driven over a smallish curb about a month ago due to another car sliding in the rain and almost hitting us. no damage was done to the car though, but I'm wondering if that has anything to do with it (I noticed a few of my motor mounts are shot, maybe something is rubbing somewhere) Any ideas...? (145,000 miles)

 

Mine makes the same noise when was the last time ya got your oil changed?

 

I changed it within 1000 miles and I changed it every time myself using synthetic oil