126 Instrument panel change
 

I just changed the nstrument panel in my 300 se with one from a 420 sel. Now my speed reading is way off. How can I fix this? Or can I simply subtract from what it says?

you can order speedo gears. use to be at www.carradio.com

1) There are no speedometer gears; the speedo is electrically driven.

2) The 300SE has a 3.46:1 axle ratio, the 420SEL a 2.47:1 ratio. The speedo heads are calibrated for specific axle ratios. The readings that are now observed can be corrected by multiplying by .71 [2.47/3.46=.71].
Example: 60 (observed) x .71 = 43 (actual)

Put the 300SE speedo in the 420SEL cluster.

Sixto
98 E320s sedan and wagon

Wow thank you guys. If anyone ever needs advice on paving a parking lot, I'm your man.

That's the quick and easy way.
 

I'd put a new set of gears on a speedometer no matter which I used. If it works now it won't long without a new set of gears.