Recently I have begun to notice a kind of rattling noise coming from under my truck. It is not constant, and I only hear it if I am in a parking lot type situation. If I am slowing down, not stopping, but slowing down to 10-15 ish, like when slowing down at a stoplight or pulling into a parking lot. it will kind of rattle up front, sounds like from the transmission area, kind of like someone is shaking, or rotating rather, a big steel baby rattle. Then it quits. Does not seem tied to anything other than slowing down. I've put it in neutral and revved it an let it drop, no sound. When I am moving I don't hear it either, except occasionally when I'm slow. When I sit at idle and try to find it, nothing. No problems whatsoever with shifting, driving, changing from D to P to R quickly, (sitting still of course), nothing. Not sure if something is just loose somewhere, but as I said I can't find the noise sitting still. I am planning on selling this thing as soon as I can return it to mostly stock, so I would like to get this resolved ASAP, even though it doesn't seem serious. Any ideas? Any questions? I will provide more specific as requested. Thanks in advance. oh, it s 2wd

 

I found a big concrete wall to drive near to reflect the sound so I could hear it. Turns out that I also hear it when I hit bumps or potholes. Something loose somewhere I think, but not sure what it might be.

 

Jack it up and just start banging on stuff with a rubber mallet, if its there you will hear it. I've had to do that a lot with my 3rd gen, fixed all the noise though!

Fink

 

You`ve described the exact sound I have to a "T". I banged all the undercarriage and came up with nothing. I did find that where the parking brake cable goes into the drum, when I grab it near the drum and move it up/down it makes a similar sound. I didn`t have any time to further explore into the drum but plan on doing it soon.

 

I think I will go at as soon as I get home from the gym. I dont have a jack at my place, but luckily like most people here I don't really need one to mess around under the truck. I'll check out that brake thing and see whats up. I may try putting my ebrake on (slightly, just enought to tension it) and see if I here the noise.
It is kind of a loud noise, but I cannot for the life of me think of what it could be. If it were IN the trans or engine, I would think it would be more muffled, and constant, or at least RPM/ gear related. I'm also gonna see if can hear it in reverse.
Jboy-how long has yours been doing it?

 

Mines been going on since around 02 or 03. When I first put the lift on it didn`t make that sound. Since it first begun up to now it has gotten a bit more louder and happens from speeds 5mph to 30mph but only with my foot off the gas. Before it was in the 5mph to 20mph (foot off the gas). Really strange noise. My solution so far is to crank up the tunes.

 

Me too. Well, time to stop being lazy and go check it out.

 

Found it!
So I got under the truck again, and this time looked more toward the front end. I hit the factory skid plate with my hand, and it kind of made a noise. I hit it hard, and made the weird loud rattle I had been hearing. Apparently, a bolt that connects the two large flat sheets of metal under my oil pan was a little loose, and it seems that the thin metal vibrating made it loud. Sounds unlikely, and I was surprised how loud it was when I was messing with it. So I tightened the bolt, pulling the two metal pieces into solid contact and took a drive through the parking lot. Based on limited testing in situations where it used to make noise, I dare say it is fixed. Quite a relief, it sounded like something big was moving. Or had fallen into something that moves.

 

It`s been a few days now. Is that sound completely gone?

 

Yeah, it's gone. Much better. Completely rattle-free. Wouldn't have believed it, but that bolt rubbing the metal was all it was.