My heat shield came off of my muffler. However the muffler seems OK. Now the shield by the cat is rattling. If it has to be replaced can I at least remove it until I can get around to installing a new one or is it something that the truck should not be driven without?

 

If it is the heat sheild that's attached to the cat itself, you can use big clamps to hold it together.
http://www.amazon.com/gp/aw/d/B00178...VhL&ref=plSrch
Like those, except bigger. That's just the first image I saw that would work. Any auto parts store will have them.

If it's the heat shield attached to the body, you can take them off. The cat and exhaust pipes get real hot, so you may feel it on the floor board though. Make sure there is no wiring dangling near by too.

 

I would try to keep the heat shield attached to the body in place for the cat, as the cat heat could damage interior flooring, particularly if you have the rubber floor. The muffler, as someone else said just make sure you have no wires, brake or fuel lines nearby, if so wrap them in some heat shielding.
If it is the heat shield on the cat body find someone with a welder and tack them back on as it is easy enough.

 

Agree with Tomb.. the heat shield is there for a reason.. removeing it is not a good idea..