How to calibrate speedo errors on your 720

[Rickie B]

My speedo was 8mph fast,the spedo would read 58mph when i was actually going 50mph according to the radar speed sign by my house,i guess this is why everybody was blowing by me on the freeway.This is how i corrected it.I got out my Garmin and set it up in the truck,drove over to the Radar speed sign to see how close the Garmin GPS speed was to the Radar sign,the Garmin was 1mph slower than the Radar speed sign,so now i know the Garmin speed is fairly accurate.1 remove the plastic bezel and plastic glass to access the speedo "needle" remove the needle by pulling it straight out twords you, it should come off very easy,"BE GENTLE".2 Drive your vehicle to 55mph according to your speed device ,now while holding that speed very carefully reach in and put the needle back on at 55,i chose 55 because it is straight up on the speedo.3 come to a complete stop and shut off motor let speedo come to a rest.4 Re test speedo with speed device,should be spot on.Now every day when i go to work and pass through the Radar speed sign my speedo is spot on,And no more cars blowing by me on the freeway.Hope this works for you

[john510]

Is it accurate at other speeds ? try going 75+ and let us know.

[datzenmike]

If 8 MPH at all speeds then (i guess) this will work. But if 8 MPH fast only at 50 that's 16 % out!!!!!! Only way even remotely possible is a transmission change

 

Has the differential or the transmission been changed that you know???

[MikeRL411]

Pressing a speedometer needle on to the shaft while doing 55 MPH sure sounds like suicide to me!

[kneesamo]

Yours is only out by 8mph!? Dang, must be nice. When i'm doing 80mph my speedo only shows 50mph.

[Rickie B]

Stock Tranny and Diff.,yes it was 8mph at all speeds Now it is aprox. 2mph off until you hit about 45 then it starts to catch up,at 55 it is spot on with the speed radar sign.i went out and tested it per a request, at 75 the radar speed sign said 76 at 80 radar said 81,so looks like its not perfect but it is a hell of a lot better than it was.we need some one else to give it a try,  to make sure mine was not just a fluke,i bet it will work.Hell when i first got my truck 6mo. ago the fuel guage would not go past 3/4 full ,so i filled it up took the plastic glass off to access the needle took my finger and moved the needle up to the full mark and now it works fine. Kneesamo ,Lake Hughes,you are not to far from me as i'me in Palmdale,give it a try

[thisismatt]

"No, officer, I wasn't texting.  I was reassembling my speedometer.  I doubt you have a vehicle code for that..."

[Rickie B]

Please no crashes,no tickets,hey i didnt crash and no ticket,probably safer than talking,texting on your cell phone,maby if you droped the needle and are looking for it,that might not be so good,now that could be ugly

[Rickie B]

First i thought maby the Tire size was incorrect,to small ,causing speedo to be faster,but tire size is correct,14"

[john510]

Stock Tranny and Diff.,yes it was 8mph at all speeds Now it is aprox. 2mph off until you hit about 45 then it starts to catch up,at 55 it is spot on with the speed radar sign.i went out and tested it per a request, at 75 the radar speed sign said 76 at 80 radar said 81,so looks like its not perfect but it is a hell of a lot better than it was.we need some one else to give it a try,  to make sure mine was not just a fluke,i bet it will work.Hell when i first got my truck 6mo. ago the fuel guage would not go past 3/4 full ,so i filled it up took the plastic glass off to access the needle took my finger and moved the needle up to the full mark and now it works fine.Lake Hughes,you are not to far from me as i'me in Palmdale,give it a try

Interesting,i would like to fix my speedo(it says 80 and im only going 65) but i just dont want to pull the needle off of a working speedo.

[Rickie B]

Dont think you can damage it,only make it more accurate,i am only talking about 720;s dont know how the needle comes off of others,i guess i took a chance when i pulled the needle off,but it worked out fine

[Rickie B]

Pressing a speedometer needle on to the shaft while doing 55 MPH sure sounds like suicide to me!

To do this in Rancho Palos Verdes it would be,maby go off a cliff end up in the ocean

[datzenmike]

This will only work where the speedo error is constant like 5 MPH out at all speeds. This won't correct for a different tire size, transmission or differential change. Yes you can correct for a certain speed but it will be wrong below or above still.

[MikeRL411]

To do this in Rancho Palos Verdes it would be,maby go off a cliff end up in the ocean

 

In all other locations it would result in a head on collision with another vehicle or a utility pole!  Or like in my neighborhood the destruction of a Chipotte restaurant under construction!  But then that was just A-H-s racing to the next red light.  Destroyed a nice Mustang when the restaurant caught fire.

[DAT510]

"No, officer, I wasn't texting.  I was reassembling my speedometer.  I doubt you have a vehicle code for that..."

HAHAHAH

[Charlie69]

Most common change to affect speedometer accuracy is tire height.

[kmc63]

I replaced the speedo gear,that inputs to the tranny,just have to find the right ratio.

[datzenmike]

Roughly, every increase of one tooth slows the speedometer about 5.5%-6%.That 5.5MPH at 100 MPH... only 2.75 MPH at 50.  Less teeth speeds the speedometer up. 

[A_Racing_Driver]

I dont even use the speedometer in my truck just use a gps because it bounces all over the place until you reach a certain speed lol

[datzenmike]

This is classic case of needing lubrication.

[kneesamo]

This is classic case of needing lubrication.

 

What do to recommend for a lube Mike?