Speedo calibration

rx7xj · August 18, 2005

I believe the tranny (4L60E) was swapped right before I bought the truck.

My speedometer reads about 10% high but using a scan tool, the ECM reports the correct speed. Is this a cluster issue or is there a way to calibrate the gauge to read the same as the ECM?

Thanks

GM-Tech · August 18, 2005

So you are saying that if you drive and the scanner data from the PCM says 60 mph, the speedo reads 66 mph?

Year? Make? Model?

rx7xj · August 18, 2005

So you are saying that if you drive and the scanner data from the PCM says 60 mph, the speedo reads 66 mph?

Year? Make? Model?

<{POST_SNAPBACK}>

Sorry about that, yes, at 40mph ECM reading, speedometer reads about 45mph. I have verified the ECM data to be fairly accurate with another vehicle.

1997 Tahoe Sport, 2dr, 5.7, 3.73 gears

GM-Tech · August 18, 2005

Sorry about that, yes, at 40mph ECM reading, speedometer reads about 45mph. I have verified the ECM data to be fairly accurate with another vehicle.

The speedometer gets its speed signal directly from the PCM (actually it's a VCM in yours I believe.... but same thing) so that doesn't leave much. If the VCM has an accurate reading, sounds like the cluster needs repairs. But I have to say, that's very unusual.

BlueTahoe · August 19, 2005

Is it off by a % or set MPH? You say 40 reads as 45 so would 80 read as 85 or 90. If it is a constant value always reading 5 mph higher then it could be the the Speedo needle is clocked wrong. Just need the needle to be pulled off and but back on at mph higher.

My 2003 tahoe computer is always about 2mph lower then the speedo. Stays constant at all speed.

Has the gauge face ever been replaced? Sometimes if someone puts a new gauge face overlay on the needle may be slightly off when they reinstall them.

rx7xj · August 19, 2005

Is it off by a % or set MPH? You say 40 reads as 45 so would 80 read as 85 or 90. If it is a constant value always reading 5 mph higher then it could be the the Speedo needle is clocked wrong. Just need the needle to be pulled off and but back on at mph higher.

My 2003 tahoe computer is always about 2mph lower then the speedo. Stays constant at all speed.

Has the gauge face ever been replaced? Sometimes if someone puts a new gauge face overlay on the needle may be slightly off when they reinstall them.

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The gauge reads roughly 12% higher throughout i.e. 90mph at 80mph reported by the ECM. Also, the odometer works correctly, it was only off by a couple of miles on a 350 mile stretch of interstate

diehrd · September 6, 2005

Is it off by a % or set MPH? You say 40 reads as 45 so would 80 read as 85 or 90. If it is a constant value always reading 5 mph higher then it could be the the Speedo needle is clocked wrong. Just need the needle to be pulled off and but back on at mph higher.

My 2003 tahoe computer is always about 2mph lower then the speedo. Stays constant at all speed.

Has the gauge face ever been replaced? Sometimes if someone puts a new gauge face overlay on the needle may be slightly off when they reinstall them.

<{POST_SNAPBACK}>

The gauge reads roughly 12% higher throughout i.e. 90mph at 80mph reported by the ECM. Also, the odometer works correctly, it was only off by a couple of miles on a 350 mile stretch of interstate

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I have the same issue.Although I know it is related to my engine and trans swap..I am sorta intrigued by your comment the Odometer is reading correctly because I have untill just this moment considered it to be 10% off just like my sped odometer. Is it possible to have a correct read on distance but not speed on a 97 5.7 vortec drive train ? ? ?

I use the mile markers on thehighway and it is frustrating as it apears distance is correct yet speed is not I just figured It was just my wishfull thinking because if my distance measurement is correct my gas milage is quite impressive ! !