Re: [Chrysler300] Speedometer calibration 60-62

The clock spring suspension end of the needle Is anchored to a post like thing that rotates around center hole like clock hands .

Spin input with drill , note reading . Say you know it is off like ten mph . That is like say distance from 1 to 2 pm on a clock , so very carefully move it ( post and Mount ) about that much clockwise (!loosens spring force) run drill again see how much more it reads etc Till it reads 10 more . Do not distort clock spring.

I am going to buy non contact tach , cheap , 25 bucks, put white tape stripe on drill , get to bottom of this . If 1000 is 60 , real rpm of drill will scale to some mph . Tach will give real speed 1-2 % .

Thinking about the scraping issue — since yesterday — (Common once cup is bent , or even unbent — fiendishly hard to get just right again) I am thinking maybe to space out the face of speedo and cup ( goes with it) by two washers . Scrape is related to in and out motion or end play of input drive , too, as magnets mount to that —spin close to cup — just too close in there unless perfect tolerance .—- i think design / tolerance flaw —-,axially too close . The one in question shows evidence of scrape on and off for thousands of miles ( that is where needle jumps up occasionally— aggravating) . Have seen that on a lot on these . Be careful not to handle it in a way that presses or rests on aluminum cup . It projects out of bottom once out of back can . Very fragile . Easy to grab it , with hand (!)! =‘slightly ‘ bending arm holding cup . I realized after that, I can position input shaft so it covers up cup there — . Protects it .

You do not get into it that deep — ,takes full disassembly to hurt it (!) - but FYI

When putting dome back do not over tighten screws . Easy to break off ears ; I have been putting flat washers there Careful, even tapping can to 6-32 . Washers Have to fit in recess , # 6 SS seem ok.

While there put Mobil one in oil inlet fitting on the thread in back . Sometimes a brass cap you pry out , sometimes a screw knob . It will not harden up . Do a few times ..

Hope that helps ..

good luck John !

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On 22 Jun 2020, at 8:12 am, John Nowosacki <jsnowosacki@xxxxxxxxx> wrote:

Hi John,
Don't think I can answer your question, but I can ask one of my own.
The speedo in my 300G seems to be off a consistent 10 mph across the range. I'm doing 80 when it indicates 70, 40 when it indicates 30, etc. Just living with it at this point, as I don't really want to mess with it, since it is so consistent and I know how much the error is in order to avoid tickets. Is that an 'easy' adjustment?

On Sun, Jun 21, 2020 at 9:59 PM John Grady jkg@xxxxxxxxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

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

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