Rattle at Slow Speed

Brother has an 11 DCLB 4x4 totally stock and he has what sounds to be a heat shield rattle right when he goes to accelerate in the front of the truck. Only happens for about a second. Being a mechanic I thought I could solve his issue but I can't figure it out for the life of me. It doesn't seem to be steering, braking, or throttle related. I checked the cat shields that mount to the floor pan, I've checked exhaust manifolds, and the rest of the exhaust system and with limited amount of time I see him nowadays I couldn't narrow it down. Since I can't get it I figured I'd ask the experts. Any ideas? TIA!

 

Had a similar issue
cat on Y-pipe “cracked” about 4 inches under the heat shield and after the crack I guess been a while the Cat started to come loose inside rattling pieces

 

Having the same issue (rattling noise developed within the last 500 miles) and after reading countless threads I'll be flipping my driveshaft 180 degrees and see if that helps, mine is a Reg cab though.

Are you experiencing any drivability issues/changes? My truck is working as it should, just the annoying rattling noise.

 

His truck works fine, before he bought it it was in a minor accident but I checked it out and the repairs check out. Its only got 120k on it too.

 

Thanks, I'll have to check that out next time I see the truck.