Need help with noise

[TMTMTL666]

Hello all,

I am having a bit of difficulty figuring this out. When i start moving there is a rather loud rattling coming from the car. This only happens when i am in first gear. If i rev the car in neutral i get no rattling. I just had the trans torn down and rebuilt which included a new 1st to 2nd syncro and a new reverse gear. I am starting to think differential but i am not sure. Any ideas??

[y87inside]

If its a manual, Id say clutch chatter. If its an auto, maybe the TC is not all the way in. Just two quick guesses.

[Takumi Fujiwara]

maybe engine Knock ?

[98Camaro3.8]

What's it sound like? Where's it coming from? Only when you go from a stop in first gear?

[TMTMTL666]

I thought about the clutch chatter, but i am not getting any feedback thru the clutch pedal that would make me think it was the clutch. If you have ever heard a catalytic that wasn't secured or heat shielding rattling that is what it sounds like, but it is doing it from a stop in first gear and from a stop in reverse. When in neutral it doesn't make a sound. Once i shift into second it doesn't do it. There is some metal shielding under the floor boards that i was thinking of pulling, but i didn't know if that would have any ill effects. Thanks for the help.