Hi there,
I've had this 03 dakota for a few months now, and for a long time I've noticed a peculiar sound from under the hood at certain rpms. It's a kind of shrill whistle, but mostly it sounds like a whine. It happens mostly just before shifting, especially in the higher gears. I can also hear it if I'm holding a steady speed at certain engine rpms. I'm not sure where exactly, tho.
I'm wondering if other people have had this problem? I'm not sure what it is, but its under the hood. It could be just something vibrating, but why?
If anyone can help I'd be grateful!

 

Hard to tell with out actually hearing it in person.
All I could suggest, is after a cold start let it whine for a while then turn the truck off.
Feel all your belt pullies. See if you have a bad bearing in your alternator, belt tensioner, water pump or AC compressor.

 

Oh, and I have checked the trans fluid. It looks fine and the level's up. Just a quick amendment to the original: When the whine happens when shifting it often gets quite loud, but even while the truck is idling or driving steady there always seems to be that slight sound. Not the simple combustion sound you like to hear.
Thanks for the reply, In2Trux, I'll have to have a look at that tomorrow.

 

Hi, I think I have the same problem as the above guy. There is a definite sound eminating from under the hood, and I think it is the idler pulley/belt tensioner. I have a 3.9 v6, so the idler pulley would be at the far left, about halfway down the pulley scheme? Should attach a pic I guess....
I've manually revv'd it with the linkage under the hood, and its definitely coming from the left side, and I'm sure its the idler pulley, but can't be 100%.
The sound also changes if I flip from drive to neutral, or vice versa, when Im going down the road. It basically varies as the rpms vary.
So if it is the idler pulley gone, would I have to replace the whole pulley, or is there a bearing underneath?

Thanks