I've known for some time that my speedometer reads slow. In other words, the car is traveling faster than indicated. Based on some side by side driving with family members I had it figured at about 10 mph off.

Today I decided to confirm that number by doing some timed miles using the mileage markers on the Interstate. I clocked it 8 different times and sure enough with the Speedo at 60 mph I cover a mile in 51 to 52 seconds every time. I don't know if the error is linear across the scale (probably not) but that puts me at around 70 mph.

After that long winded preamble, my question is: How is it that these mechanical Speedos get calibrated? Is it just slop in the plastic gears? From, in my case, 418,000 miles of spinning? If so, will replacing the gears with new bring me back close to spec? Or is there some other secret adjustment?

Just wondering if sending the cluster out to one of the shops that works on these things is the way to go or if I can get it fixed by replacing the gears myself?

__________________
Joe

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1980 300SD - 495k miles - 'The Ambassador'
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Former Family Members
95 C280
73 280SEL
90 300D
87 300SDL (X2)
86 560SEL
84 300D
80 300SD