auto transmission won't shift and rpm& speed guages don't work

Discussion in 'GMC Truck Forum' started by gmcer, Apr 13, 2005.

  1. gmcer

    gmcer Member

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    The two guages and the transmission not shifting by itself both stopped working at same time. I bought a new transmission three years ago never had any problems with it. I took truck into a good place to have it checked and was told its not the transmission but probably something to do with something in the electronics. He hooked up a computer to my truck just to see if it was reading a rpm signal. It did. It just was not reaching my my rpm gauge. So somehow the 2 gauges not working and the auto transmission not shifting are somehow connected somewhere I guess. I can still drive the truck but I have to manually shift from second to third to start or I just leave it in third. First gear and Drive don't work right now either. My wife was driving one time and she said the gauges all of a sudden started working for just a min and the truck auto shifted fine before it went back to not working. Does anyone know what is causing this? I've heard it could be the computer itself or something called a vulcan module ( i think that what it was called). Any ideas and if it is that module is it a fairly cheap item and where is it located?
    My truck is a 1995 gmc sierra 350 5.7L 4x4 1500

    Also I broke the door handle. where can I buy or do I have to go to dealer?
     
    Last edited: Apr 13, 2005
  2. Dax

    Dax Senior Member

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    I would try going to a junk yard first. We call them Pick&Pulls. It would be a lot cheaper and you could find that door handle.
     
  3. mrjohnwayne

    mrjohnwayne Full Member

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    If your truck is not starting out in 1st gear then quit driving it. Starting out in 2nd is a very good way to sending yourself straight to the shop. What year is the truck, and do you know what kinda tranny it is. 700-R4, 4L60E?? yes they are the same but they do have major differences.
     
  4. chevynut

    chevynut Full Member

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    which guages are not working,if speedometer,replace speed senser on transfer case.
     
  5. gmcer

    gmcer Member

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    its the speedometer and the rpm gauge. would this sensor be causing the truck not to shift or start out in first? I can manually shift from 2nd to third but that's it.
     
  6. chevynut

    chevynut Full Member

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    usually that is a A solenoid problem,but I have never seen a bad A solenoid cause the guage problem. The problem with the gauges could cause the shifting problem,and if I were to try to fix your truck if it came into my shop, first thing I would replace is the ingnition switch (under the dash),thats where we have found the most problem.
     
  7. gmcer

    gmcer Member

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    Ok, I'll Try Replacing The Ignition Switch And See What Happens. Where Is This Solenoid And Should I Replace It Too? I'll Hold Off On The Speed Sensor For Now. Probably Won't Need To Replace It.
     
  8. Moostang

    Moostang Senior Member

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    While you are under there, see if you are getting both power and ground to the guages I imagine you are not, then trace it back to where you get power.
     
  9. silvervortek200

    silvervortek200 Full Member

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    Id start by checking all fuses and the wiring harness going into the tranny. Check your battery terminalsare they clean and tight .
    Sounds like a bad earth wire or a loose wire or connector some where.
    With ign turned on i would feel around under dash checking/feeling wires and connectors while keeping an eye on the gauges. if the flash on its probably just a wiring connector loose. I have a feeling its a loose earth some where good luck hope this helps.
     
  10. Justtrucking

    Justtrucking New Member

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    Trans 4L80E concern

    I recently came across the same problem with a costumers Trans 1995 2500 chev 2WD 4L80E. Checked codes - converter clutch related concern?? Checked all-data info. TSB concern for vehicle was related to a EPROM udate. A concern with trans not shifting within 2 seconds of command . The new Eprom has a 4 second delay to allow for delay shift. I have not yet installed the new e-prom. Was going to check wiring due to the fact that when you clear the code the transmission shifts normal. When the Tach and speedometer start to drop or do not read is when the transmission goes into default mode and does not shift out of second gear . This a weird one . Have contacted GM - they have heard of trans concern - but not the gauge fluctuation concern. ???

    These electrical concerns can be frustrating
     

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