Hey guys. After a few years of on and off tinkering, I finally solved a very obnoxious vibration/harmonic that originated under the hood but could be felt through the seats and pedals. It occured around 2400-2600 rpm (60-65 mph in OD), after the car had warmed up, and became quite loud after traffic light driving. I recently had to replace 3 water pumps (5k miles apart) due to bearing loss, and I got to thinking what could cause this. The belt was not overtightened, so the only thing it could be was the fan clutch. So, $70 later, I had the new fan clutch on the car and, guess what, there is no more harmonic/noise. Several shops claimed the noise was an exhaust harmonic, but I just wasn't buying it, being the problem only occured when the car was warm. My car is a 1989 760 turbo with 211k miles. I have come to understand the clutches are a weak point, but I didn't think this was a typical failure mode.
Off the subject, but curious, has anyone found a source for independent rear suspension bushings for the IRS cars? IPD does not stock them, and Volvo wants and arm and a leg. Anyone?

Regards,
Jeff