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Anonymous Posted on Feb 21, 2018

I have a 1989 GMC C1500 1/2 ton pickup truck with a rebuilt tranny and an aftermarket 350 small block engine. The total mileage counter and the speedo doesnt work. We bought the truck used at an auction and we are trying to fix the speedo and tachometer but cannot figure out whats wrong.

1 Answer

Denis Houle

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  • GMC Master 1,414 Answers
  • Posted on Feb 23, 2018
Denis Houle
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You have so many problems but not much to work with. Let's try something to help you out.
1. Instrument panel is it Analog or Digital
2.For speedo and tach do you have a speedo cable attach to the cluster?
If it's with speedo cable. Inside the transmission, there is a plastic gear could be worn. And the cable at the cluster's end could be stripped or not install properly.
If it's with the digital cluster the speedo works with a buffer module near the glove compartment (It convert the analog signal to digital signal for a digital cluster.
I could tell you more but need too many info.
There is many instrument panel depends on the options.
See options: links

Hope it helps.


I have a 1989 GMC C1500 1/2 ton pickup truck with - sliveradoclusterwithtach-qrapc2eyzd0qf0shbbxh4pv4-3-0.jpg

s-l1000-qrapc2eyzd0qf0shbbxh4pv4-3-4.jpg Find out instrument panel pinout (or electrical diagram) for wires testing.

1. There is more ground than only one and there more + wires at cluster panel. I will have to check those circuit and finally find the problem.

5 Related Answers

Anonymous

  • 321 Answers
  • Posted on Nov 28, 2008

SOURCE: Speedo stopped working and tranny wont shift out of first!

I will try and clear up any confusion about the different model designations.The trans was first introduced as the Turbo Hydramatic 700 r 4.Later in the evolution of that family,it had improvements made on it by the factory engineers,and they redesignated it the 4L60 model.The 700/4L60 uses a throttle valve cable as a mechanical indication of the throttle position....to the trans.The TV cable regulates mainline hydraulic pressure inside the transmission.This model also uses a governor as a road speed mechanism.It is responsible for the TIMING of the upshifts,and is responsible for the trans being in first (low) gear from a standing start.In 1993,the 4L60E was introduced to the lineup.Same trans as the 700/4L60,but now it is totally electronic,and totally controlled by the PCM (Powertrain Control Module) based on electrical inputs/outputs from the trans,throttle position sensor,road speed,etc.The engineers took the 700/4L60 and did away with the governor and TV cable,made it totally electronic.Early 700's had a mechanically driven speedometer,while the later 4L60's and E's had an electronic speedometer.1993 was a transition year.I have seen both,the 4L60 and the 4L60E in 1993 model trucks,it depends on the month of the manufacture of the vehicle.Your truck could have either,or.The way to visually identify the difference is........on the driver side,the 700/4L60 trans case will have a round,black,governor cover,about 3 or 4 inches in diameter.The 4L60E case does not.The 700/4L60 also has the TV cable mounted on the passenger side of the trans case,and it routes up to the throttle body/gas pedal/accelerator linkage.The 4L60E does not.Recently,the 4L65E and 4L70E versions have been put into production.Based on your description of the malfunction symptoms,i would be inclined to say yours is probably the 4L60E version,because the speedometer malfunction occuring at exactly the same time as the shift malfunction.On a 700/4L60,the speedo malfunction would have no affect on the upshifts,the trans would operate normally.On the 4L60E,a speedo malfunction would likely cause no upshifts.You should still visually verify by the governor cover,or lack thereof,on the side of the trans case.It could just be a speed sensor malfunction if it has the "E" model.If so,it would have set a trouble code which can be accessed with a scan tool or a code reader.Hope this eliminates any confusion.Good luck!!

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Anonymous

  • 1 Answer
  • Posted on Jan 11, 2009

SOURCE: aftermarket tachometer in 91 cavalier???s

purple/white off the ignition module is your tach signal

Anonymous

  • 585 Answers
  • Posted on May 08, 2009

SOURCE: Install aftermarket tachometer

I'll take a stab at this, there's better than a 50-50 chance, and you can do no damage if the first try is wrong. Red is +12 volts and Black is chassis ground. that's a given. I would try Blue to coil pack "Tach" terminal, and Green for the dashlight. If I am right about the Blue and Green, a 9-volt battery from Green to Black will light the light if it's not burned out. If the Green doesn't light it, try the Blue, but my bets on the Green. If the Blue doesn't light it either, the bulb is toast.

Anonymous

  • 1 Answer
  • Posted on Jun 07, 2009

SOURCE: Speedometer does not work 1991 GMC Sierra 2500

the turbo 350 doesn't have a output speed sensor like the trans that came with the truck orginaly. You will have to use a cable to drive a pluse generator,or switch the tail shaft housing with a 700r4e housing of the same length,and use the speed sender from the 700r4e or early 4l60e. note the tail shaft is the same splines but the 350 shaft detent hole my not line up with the relucture ring. therfor the output shaft needs to be change to, or have a relucter ring made.

azmas

Azhar Mastan

  • 90 Answers
  • Posted on Oct 09, 2009

SOURCE: Hi my speedo works but the mileage counter does not turn over

1. The plastic gear inside may have broken. Replacement kits are available.
2. Check the floater and the sensor above the fuel tank. Wire harness may be the culprit.

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