I let my 16yo drive [attempt] to the '05 TL to the driveway. After jumping the curb and nearly hitting a parked car, there's a lot of rattle as I drive over the smallest bumps and manhole covers, and when I put it in reverse, there's a lot of noise and rattle. I was hoping I didn't mess up the tranny because there is a small leak of clear fluid from under the car. I wouldn't think condensation would be that far back but what would I know.

Then I jacked the car up...bent heat shield and missing bolt. Does the bolt go to a motor mount? Either way, what would be the part number for that bolt?

 

Looks like a subframe mount and I don't think you are missing a bolt there. It is number 8/9 in link below and only has 2 bolts as you have. If you put a bolt in that other hole you would negate the whole isolating effect of the mount.
Acura Parts @ AcuraOEMparts.com - Genuine Acura OEM Parts from Delray Acura

Clear fluid would not be transmission fluid. That would be red or brownish. Did it smell or feel greasy? If the spot on the pavement is gone today (assuming no rain washed it away) it was likely water. If it pavement is still stained and greasy then could be power steering or brake fluid. Those will typically be yellowy/brown but could look clear if very new.

FWIW I would look for any scrape marks on the bottom and start there and move outward. DO NOT do this unless you have jack stands and are confident the car is stable on them. Never get under a car just on a jack.

 

It might well be water from the AC too, since it's near the front right wheel. As Adobeman said, look to see if it's an oily residue.

 

Ditto on subframe and likely condensation from AC as I'm sure it sat there until you were able to move it.

You'd have apparent damage to your radiator front end if the heat shields on the pre cats were damaged as a result, there's about a fist width between them.

How much of the car went over the curb? Or did you son get it off before you got to it? Adobeman is on the mark in looking for fresh scrapes. I don't see any in second pic conclusive of reaching the bend of the j-pipe, that would be thrashed. You'd see scuff marks all over the plastic guards underneath too.

but, it could be possible the rattling is in fact the heat shield, just from the impact shifting them, as they do have a certain amount of play in them. Mine rattled and I was able to shift it a little and resolved it.

I'd assume the left driver's side tire hit first from your markings of the road. Could've broken a suspension component like an end link or ripped some bushings somewhere.

If no indications of fresh scrapes, and the driver's side tire hit first, I'd take that tire off and inspect the suspension components next.

 

Thanks all. There aren't any scrapes after taking a second look.
What would cause the transmission rumble when going into reverse?

The kid hit the curb w/ on the passenger side.

 

Could be an exhaust pipe is bent and touching the frame, or one of the rubber exhaust hangars broke, allowing the exhaust pipes to move more than normal. That could transfer a lot of noise and vibration through the car, and would also account for differences in the noise and vibration depending on whether you were in drive or reverse.