Ok, I've had my '97 SD since new. 100% stock. The other day a strange rattling started under the hood. Random kind of grinding, rattling noise.
Mainly at idle, no load. I can put on parking brake and in drive/reverse, it doesn't rattle. Neutral rattling.
Took off belt to insure it wasn't an idler/brg up front. No such luck. Took off the Y manifold from the turbo to see if I could tell if it was causing noise. Nope, still there and not louder. Doesn't sound like lifter, or engine (internal) issue. Transmission? What rattles in an Automatic? Drives fine, good power, no hesitation, no change in performance. Checked fuel, no water.
I DO have minor fuel pump leak, could it be pump rattling? Any suggestions? Ideas to where I should head? I really HATE to take into shop as this kind of thing is a stealer's dream.

 

If at all possible, it would really help us if you could post a video or audio clip. You don't necessarily have to post it on these boards- upload to youtube and link us to it.

Otherwise, I would suggest putting the truck up on jack stands [all 4 wheels off the ground], then running it to produce the rattling and crawl underneath to try and find it.

I'm not familiar with the 97's so that's the best advice I can give.

 

check for loose heat shields... they rattle eventually

 

Just throwing this out there, but it sounds similar to another thread on here, that was discussing the possibility of a cracked flex plate. I don't have an experience with that, but maybe someone else can chime in.

 

Just to complete this thread.....
Took truck into dealer. I know, expensive option, but not having any references into Ford service in this area, I felt it was best choice. Flex plate or torque converter. Well the Flex plate was almost broken just outside the bolt ring where it connects to engine crankshaft. Would have been bad news if I'd sent my wife on the 400 mile trip she's doing this week.
Maybe I can get a few more hundred thousand out of it now!

 

I was gonna say cracked flexplate too. just read this thread. Glad to know that you found the problem since both you and your wife would have been very disappointed when it broke FAR, FAR AWAY from home!

 

Wait, you noticed a rattling in a diesel? Like an extra rattling? How could you even hear it?

 

When I kept getting a rattling, only at idle/light take-offs it'd drive me up the wall, and down the other side.

I came to find out it was the support arm for the EGR tube. Was suppose-to bolt somewhere, but a 12" zip-tie has taken care of that rattle =P just something else to look into for anyone looking at this.

 

That's just the thing.... I've had, for probably 2-3 years,maybe longer, a noise that wasn't loud, but it was THERE, when I decelerated. Foot off the accelerator, down around 15-25 miles per hour, diesel was idling and you could hear kind of a ticking. Not loud or what I would say was something I was concerned about, but it definitely the flex plate. It ultimately, in a very short period of a few days, went to a really bad rattle. If anyone is driving an auto, and you hear ANYTHING other than the engine idling when you slow down, I'd say you probably have flex plate damage.

 

You did the right thing. Congrats on your courage and forsight. I salute you.