There is a rattling when i start the truck. its also loud when in first gear to second. sounds toward back of truck. exhaust?

I suggest you have your car checked as soon as possible - while a rattling exhaust isn't desperately urgent it could be the cat breaking up which might later restrict the flow of gases. Most importantly excessively loose timing belts or chains tend to make most noise when the engine is idling. If the noise is being caused by this delay could be very expensive.

Pull the valve cover off to check for rocker arm. Could be exhaust leak if more of a popping sound than a rattle.

hi this sounds like to me you might have a loose baffel in the box, the reason why the sound dissapates when you get to a certain speed is because the baffel is pushed up or down due to the pressure when you slow down the pressure then releases the baffel and it starts rattling again, you might also have a broken clamp on your exhaust or even a missing rubber bush check these out first...good luck

Check to see if one of your brackets holding the exhaust pipe has come loose. That'll make a rattling sound - especially if it towards the end by the tailpipe. When you're accelerating - more air is forced thru your exhaust at a faster rate, so it's not moving as much as when you're sitting still and the truck is just at an idle with less air/exhaust moving thru the tailpipe. If it's only making the noise while the truck is stationary & the noise stops one the truck is moving - that pretty much rules out anything to do withe the drive-train or suspension. You are sure the noise is from the back & not coming from under the hood? If under the hood - check your oil level ASAP.

Maybe its an exhaust rattle?

Check all braces under your car. Not just visually, put hands on each and every brace. Sounds like one might be loose or broken. Hope it's as easy a fix as mine was.

your exhaust IS plugged. you need to find out where. the cat would have been first however in this case.....what else in down line from the manifolds?

sounds like the flex plate on the back of the torque converter has splt across the bolt hols that hold it to the crankshaft

4.0l's are notorious for valve rattle on cold start-up. There is really nothing you can do to make it go away short of completely replacing the valve train in the top end, and that isn't a permanent fix. It's is an top end oiling issue from the factory. Just don't race your engine on cold start-up until the rattle stops.

The rattle in the transmission sounds to me to be more of a loose dust shield/heat shield around the transmission or exhaust than a mechanical issue.

water pump by teh sound of it seal ok but bearing going