I have a 1985 300SD turbo diesel with 309k miles. I have just notice a clicking noise that is coming from the right front area. The clicking frequency increases with wheel speed, not related to engine RPM. It's like there's something sticking into the slots in the rim that makes a 30 clicks for every wheel rotation (I already checked, there isn't anything). Once above 40 - 50 mph the clicking is so fast that it isn't discernable anymore.

I first thought wheel bearings, but putting the bearing under lateral loads doesn't change the noise at all. I don't see anything that would be rubbing against the tire or rim under windload, plus since the clicking starts from a stop there's no windload to deflect anything yet. The noise seems to be forward and right of the transmission so I don't think it's driveshaft related. It could actually be comming from under the passenger dash-board/firewall area, but I don't know of anything inside the car that would be wheel speed related.

Any ideas?

Thanks.

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1985 Mercedes-Benz 300 SD 309k miles
2003 Mercury Marauder 300B Blue
2006 GMC 2500HD Crew Cab/8' Bed; 21.5' long
2002 Pontiac Bonneville SLE