Rattle at start up plus 1st and 2nd gear

This just started yesterday, kinda sounds like a heat shield that is loose or something. It makes the same sound when starting off from a stop just as I accelerate in 1st and 2nd gear. I also noticed I have a vib at 72mph that has gotten a little worse but goes away at 77mph but that is probably unrelated. I did just change the oil and filter plus rotate the tires.
Thanks for any help/ideas.

 

Peoples definition of a rattle are hard to understand. Our cats make some weird noises when we accelerate if you are talking about that.

See what the dealer says.

 

Ive heard something recently that sounded the same, like a heat shield or something thin metal rattling. I have an automatic though. Mine sounds like its coming mostly from the drivers side engine bay.

 

could you have possibly damaged/bent the brake dust shield when rotating the tires ? that would be the first possibility since you just rotated your tires before it happened.

ive had the heatshield on one of the secondary cats rattle around every now and then . i just removed them .

i have also had the bracket bolts that attach the exhaust mani to the bottom of the block come loose a few times and rattle around . i have started using lots of red locktight and more torque than recommended to get them to stay

 

Thanks for the ideas, I'll crawl under and have a look. The oil change and rotate was about a week ago before this started, I think the vibs at speed are just the crappy Dunlop tires. The rattle sounds like a bunch of rocks in a coffee can but not engine knocking, it's much faster

 

Well its the front catalytic converter for sure, and I don't think its any of the heat shields because I can't make it stop by applying pressure with a wooden broom stick. With only 15K on the truck is it possible it went bad on the inside? I have never run any chemicals in my gas either. The other thing I have noticed is that I lost 2 MPG's on my fill up today, related?
Thanks,
Ron

 

Just an update, last Friday the dealer replaced my entire mid-pipe. Something let loose inside, glad its fixed the rattle was driving me nuts.