[Chrysler300] Speedometer calibration 60-62

["John Grady jkg@xxxxxxxxxxxxxxxxx [Chrysler300]" <Chrysler300-noreply@xxxxxxxxxxxxxxx>]

I got into 3 speedometers over the weekend ,60-62 type ,long story but good now .Even all 12 gauges now work. And pointers light 
If l recall correctly (and may have written about this ) all speedometers are calibrated such  that       1000 rpm on cable into head is , I believe ,  60 mph? Why trans drive gears vary .  
I have a dewalt drill that is 500 on low speed range and so should be 30 mph . However two of the three are non letter car 120 mph units ( well mangled before I got them  , including one with needle shaft snapped right off . ) — these things are a bear once someone bends the little magnet cup off center . And it scrapes ... 

To cut to it , the real F one ( 150 mph) shows 25 mph at 500 , ( not 30) about 90 at 1700 ( High speed on dewalt but probably not accurate ) ; the undisturbed  120 speedo calibration shows 75 when the F shows 90 . This got me thinking whether 150 and 120 are different in this rpm / mph thing . Probably not ( 1000 rpm is 60 mph ) . It is just all of them have been mangled ??  Any Thoughts ? 
Hard to get it out later , would like this to be right. 
By way of info , eddy current force in aluminum cup is proportional to speed and clock spring parameters must be close  ( spring constant ) to resist in a way that is linear in the reading . So zero set is meaningless , it will generally return hard  still pushing against  zero stop , and the adjusting spring start place , right off stop should shift whole range ( the calibration ) but 150 mph F probably has special stiffer spring as the increments are obviously closer together . Calibration cannot change that spacing . Or ? weaker magnet . Not sure .   
By the way never force a frozen speedo head ( they all freeze up if stored) as you may strip the first odometer drive gear ( nylon) which will make you very very sad... !  Have to remove odometer drive then free , unless feeling exceptionally lucky 🍀 
John 

Sent from my iPhone not by choice 

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Posted by: John Grady <jkg@xxxxxxxxxxxxxxxxx>
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