I'm hoping that this should be an easy one.

There is a rhythmic, low pitched rattling that seems to be coming from the passenger side dash area. It does not vary with engine RPM (as in, revving the engine does not affect the noise) and does not happen all the time. It usually kicks in after a few minutes of driving, and particularly after downshifting. But, I highly doubt that it is transmission related. Any common problems I don't know about? Thanks.

Info-

1996 single cab short bed, 3.9, 5 speed manual

Loose idler arm, but pretty sure that's not the problem

 

if it's inside the cabin all I can guess would be a vacuumed controlled damper maybe fluttering due to a slight vac leak. Easy enough to check...plug the vac line into the cabin.

 

I'd also empty out the glove box, and try it with the door open and closed; it could be something in the glove box rattling!

Also, you didn't state if 2WD or 4WD; but if it's 2WD, it doesn't have an idler arm.

RwP

 

Another thought, could your exhaust system be touching the frame, or could you have a broken motor/transmission mount? Downshifting may torque the drivetrain enough to instigate some metal-to-metal contact.

 

That could be. The manual dakotas have a lot of clunking issues (as per all the TSBs about it) and I know that the tranny mounts come apart like tissues. My transmission will thump the floor if I get on the gas too hard. But the noise doesn't seem to be coming from the undercarriage, and the pitch of the noise sounds more like plastic than something metallic.

 

When it happens is the heater turned on? My experience with low rythemic(sp?) Rattled has either been the blower motor rattling or exhaust heat shields but the heat shield is more metallic and the blower is plastic