rob8

I only just noticed this when finally able to drive with the top down on my 2003 W208 cab. A second or so before each upshift, the is a noise like a chain dragging on the ground coming from underneath the car. Once in top gear, no more noise. The car still shifts smoothly and at the right time, and you can't hear this with the top up, so it isn't really loud. Any ideas what this could be? It definitely isn't pinging from the engine.

rob8

No One? It's getting worse!

02tahoeindiana

Does this sound occur at a certain rpm each time? My cats rattle at a particular rpm and its noticeable before shifting at about half throttle and its quite loud

rob8

It happens right around 2300 RPM, just before it upshifts, and is most noticeable under partial throttle.

02tahoeindiana

It sounds alot like the same noise im experiencing but hopefully others will chime in. Mine is very noticeable with the top down and I can even hear it over my straight pipe exhuast, although it does no harm. If its shifting and running fine with the noise I wouldnt worry too much.

Gundo

Have you ever heard the noise while you are not moving but in drive? Like at a stop light or ordering at a fast food drive through?

Have you visually inspected underneath the car for anything out of place? Inspected your shifter linkage bushing?

rob8

It only happens when I'm moving. I'll take a look under the car tomorrow.

GatorMB

Possibilities are the driveshaft center carrier bearing support.

Driveshaft coupling, Transmission or Engine mount.

Exhaust hangers.

When a drive shaft flex disk (coupling) breaks away it can total the car.

Gator

jonUF02

Check under the car, flex disc, mounts, etc. bang on the cats a little with a rubber mallet to see if they rattle. If it's the rear cats, then just cut them out and move on unless you have stringent emissions testing where you live.