My speedo is off...how do i fix it

[ivorton74]

I got pulled over today in my truck..i was doing 55 mph but the cop said i was actually doin 63 mph...i didnt believe him so he showed me the radar gun and it was 63. So i got my gps and went for a run and it reads correct until i get past 20mph and then its all wrong...for example when the speedo reads 35 the gps says im doing 42. Im running stock size tires 235 75 15...so how do i correct my speedo? Now i have to drive with my gps....im just glad i just got off with a warning...i dont want to get no tickets for this.
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[geezer#99]

You can change the speedo gear or the drive gear in the tranny or just get the right ratio adaptor. All those parts are here.
http://www.transmissioncenter.net/sp...____va.htm#350

[hrc200x]

I got pulled over in South Dakota two weekends ago for doing 5mph over, 80 in a 75, SD state patrol must be crackin down. Very nice cop, just a warning here too.

[bnoon]

Actually ivorton74 to me it appears as if you are right at 7-8 MPH off at both speeds. If you had the wrong transmission gear it would be a percentage off, not a set MPH off at all speeds. Someone messed with the needle and just moved it on the pin.

My speedometer was 28% off, so at 35 MPH indicated I was actually going 44.8 MPH, or reading 9.8 MPH slow. At 50 I was actually going 64 MPH, 14 MPH slow. At 100 it would have been 128 MPH or 28 MPH slow, which is 28%. See how the error gets larger as speed increases? I got lucky and found the correct adapter in the salvage yard.

[tlawre87]

Originally Posted by bnoon

Actually ivorton74 to me it appears as if you are right at 7-8 MPH off at both speeds. If you had the wrong transmission gear it would be a percentage off, not a set MPH off at all speeds. Someone messed with the needle and just moved it on the pin.

My speedometer was 28% off, so at 35 MPH indicated I was actually going 44.8 MPH, or reading 9.8 MPH slow. At 50 I was actually going 64 MPH, 14 MPH slow. At 100 it would have been 128 MPH or 28 MPH slow, which is 28%. See how the error gets larger as speed increases? I got lucky and found the correct adapter in the salvage yard.

x2 on this. On my old ZJ when I went to a 31 I found each 10mph incriment was a mile off (at 20, doing 22...60 doing 66, etc)

Sounds like a speedometer whether its been pulled or a cable. My old ranger was kinda the same. It was a bad cable.

[ivorton74]

Well it looks like i gotta get my transmission checked out...it slips in second gear a bit and vibrates a lil bit on take off...i topped off the fluid yesterday but still slips...so im thinking it may be time for a 700r swap or i can just start my 5.3 swap now.
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[cory d]

i have been about 30% off after swapping out my th350 for my sm465. been like that for like a year. havent thought about fixing it haha.