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how to calibrate a speedo for new gears

jprather

jprather

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Hi all,

so i finally got my new rear end.. going from a 8 1/4 2:73 ( ?) to 8 3/4 3:55 sure grip, how do i re-calibrate the speedometer ???
 
i'd start with the basic factory combo. factory was 35 tooth for 15" wheels and 36 tooth for 14" wheels. you can fine tune from there.
 
speedo 002 (Medium).jpg
 
It's a small shaft with a gear on it that attaches to the end of the speedo cable where it goes into the transmission.

I believe Cranky was selling some on here.
 
i have 15" wheels !

thanks all, i will see if i can find " Cranky " if not i guess year one or summit or the like will have ?
 
oh, i guess i should have added this... 727 trans, 15 in rims with 275/60 R 15's !
 
looks like the yellow 33 tooth, any one have a spare ?? man those are expensive at year one !
 
Fyi- these bushnell radar guns work pretty well for checking your speed when calibrating your speedometer.

I bought mine for about $100 a while back

untitled.png
 
hoover said:
Fyi- these bushnell radar guns work pretty well for checking your speed when calibrating your speedometer.

I bought mine for about $100 a while back

View attachment 593534
Click to expand...

i have been using my phones gps with speed checker or something like that , it even has heads up display, set it on dash board and it projects on to windsheild
 
I bought a new one on Ebay recently. Came with set of O-rings and all for the gear adaptor. FWIW I went with a 34 tooth on 215/75-15 tires and checked it with a phone GPS. It looked to be traveling about 49 mph for an indicated 50 on the GPS. Any smaller dia tire and I may have to go to a 35 tooth gear.
 
I'm going to use this app. on my cell phone to check my speed. I checked it against my Sebring on the way home one day and it's right on the money. You have a short period of time to use it without adds popping up.

I'll only need it just to check how accurate my speedometer is, after changing rear gears and changing the gear on the cable. I'm still waiting on my registration to be approved so I can take her out for the first time.

Its called "Speedometer" and works off your GPS...
20180411_130754.png


20180411_130820.png
 
I used a GPS app to check my speed and uninstalled it once I verified I had the right pinion gear. Those apps are free for a reason. UNINSTALL it immediately after you get your results. Unless, of course, you want to be tracked everywhere you go with your phone.
 
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