Speedometer running fast

[JWW67]

Hello all,
I have a 93 Chevy Chyenne with a 4.3L engine. My speedometer is running about 10MPH fast when at freeway speed. The truck has factory rims and the tire size has not changed. Anyone have an idea what to check? I'm thinking maybe the vehicle speed sensor?
Thanks in advance.

[Blue Bowtie]

It could be the VSS, transmission, rear axle, or the ECM programming. If the transmission has ever been repaired or replaced the reluctor in the tailshaft could have the wrong tooth count. If the axle has ever been changed the ratio would need to be corrected in the ECM programming or VSS tone wheel (reluctor).

If the setup is completely original, the VSS face could have contamination, the VSS circuit could have poor connections at the sensor or at the VSS buffer module, the buffer module could be damaged, or the sensor itself has problems. Any of these can cause the system to generate more pulses which is interpreted as higher speed. The VSS buffer module should be located on the rear of the I/P near the right side.

It could also be a problem with the instrument panel indicator mis-reading pulses from the VSS system.

[j cAT]

Originally Posted by JWW67

Hello all,
I have a 93 Chevy Chyenne with a 4.3L engine. My speedometer is running about 10MPH fast when at freeway speed. The truck has factory rims and the tire size has not changed. Anyone have an idea what to check? I'm thinking maybe the vehicle speed sensor?
Thanks in advance.

not a normal failure ..
I suspect this is from the previous owners work changing parts that effect speed indicated. if the speed increasing in error the faster you go then that is the problem. a bad sensor will not do it.

smaller tires / rims will also get this effect , the the speedometer will indicate higher speed than actual. GPS is good at checking this error..