weird rattle under the bed when i let off the gas

well iv finally started driving my 99 taco and i had the rear shocks done since the last time i drove it. it has quieted up the back end tremendously. but now im left with a freaking loud rattle/squeak coming from behind the cab under the bed. that is only present when i let off of the throttle and kinda goes away a little while braking. and it does not occur at low speeds. it was most likely there before but couldn't hear it as well with all the rumbling driving on blown shocks makes.

the noise sound almost exactly like my mini bike exhaust does where the slip joint on the exhaust is rattling. i did notice before that my truck has a slip joint in the exhaust but i do not remember one in my 01 taco i had previously. there is also soot all around the smaller diameter tube.

i wonder if that is the noise i am hearing...my thinking is that it only rattles when back pressure is low..meaning while i am accelerating or maintaining freeway speeds the exhaust pressure keeps it from rattling but when i let off the gas the exhaust pressure decreases allowing the rattle to happen.

basically my main question for you guys is what do yall think? and is there supposed to be a slip joint in the exhaust piping? i can go get it welded tomorrow if its not supposed to be there. the exhaust does sound modified but looks stock as far as i can tell.

my only other idea is rear brakes??

thanks in advance for any ideas guys.

 

The stock exhaust on my 04 was a solid welded piece from the second cat to the end. I put on a magnaflow cat-back and have the same thing you describe because I couldn't get the clamps on tight enough on the muffler. Been meaning to fix it, for 5 years...

 

be sure to check the center support bearing. when it starts to go, it can cause a lot of weird sounds and vibrations.

 

thanks enigma that helps me confirm my thoughts...and @ space wrangler, where and what exactly is the center support bearing? id be more than willing to inspect it as i am trying to get this truck running like new again.

 

You will see the center support bearing if you just follow the drive shaft from the transmission to the back diff. It's what holds up your drive shaft. With a split drive shaft it holds up the first part of the drive shaft before the joint. Grab the drive shaft a few inches from the center support bearing and check how much free play. About 1/2" is acceptable.

If you still cannot find it, let me know and I will get you a photo.