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Speedometer

Tiny
PACHYAUTO63
  • MEMBER
  • 2000 GMC C3500
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
Is there a p-sensor in the transmission? I replaced all speed sensors and neutral switch, but when I drive the speedometer goes crazy up and down. What is going on?
Friday, November 17th, 2017 AT 8:45 AM

5 Replies

Tiny
F4I_GUY
  • MECHANIC
  • 3,302 POSTS
When you say you replaced all speed sensors, which sensors are you referring to? Did you replace the vehicle speed sensor located on the transmission output side or the wheel speed sensors located at each wheel?
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Friday, November 17th, 2017 AT 1:34 PM
Tiny
PACHYAUTO63
  • MEMBER
  • 40 POSTS
Transmission output side.
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Friday, November 17th, 2017 AT 1:55 PM
Tiny
JIS001
  • MECHANIC
  • 3,408 POSTS
Is this an automatic? Also is the truck 4 wheel drive? If automatic do you know which transmission you have on here? Is it the 4L60E or the 4L80E?
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Sunday, November 19th, 2017 AT 6:20 PM
Tiny
BARBARA1963
  • MEMBER
  • 99 POSTS
4l80e
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Friday, November 24th, 2017 AT 1:29 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,973 POSTS
The speedometer output signal is generated by the PCM but my guess is the speedometer is bad though is the connections are all good. Try to remove the cluster and remove the connector then plug the connector too in to see if it was a bad connection.

Here is a video how on to do it.

https://youtu.be/_HEC44xENxw

It also shows a rebuilt cluster getting installed.

Please let us know what you find. We are interested to see what it is.

Cheers, Ken

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Sunday, November 26th, 2017 AT 6:54 PM

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