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1997 gmc sierra 3500 won't go over 98km/h

Discussion in 'Truck & Equipment Repair' started by duramax-king, Jan 2, 2010.

  1. duramax-king

    duramax-king Senior Member
    Messages: 134

    hi guys i bought a 1997 gmc sierra 3500 not to long ago and i was told it needed a tranny shift cable, so i replaced it and tried it out on the highway and it still won't go over 98km/h, does anyone kno what this could be?
    Sorry it's a 6.5 turbo diesel with auto trans.
     
  2. CT-TILEMAN

    CT-TILEMAN Member
    Messages: 61

    There is a factory speed limiter, it will need a custom ecm reflash to remove the limiter.
     
  3. VPRacing

    VPRacing Member
    Messages: 74

    98km/h is like 60mph... Theres no way it would have a 60mph governor.

    Is there a factory tach? If so, what RPM is the engine running at that speed? Sounds like it could be something to do with the trans cable in a lower gear. Although I thought they had shift linkages???
     
  4. no lead

    no lead PlowSite.com Addict
    Messages: 1,308

    sounds like your not shifting into the final gears.
     
  5. duramax-king

    duramax-king Senior Member
    Messages: 134

    i replaced the linkage that shifts to the tranny, and it shifts into all gears.does anyone kno where i can get a custom ecm reflash, or other way to remove the limited.
     
  6. Steve G.

    Steve G. Senior Member
    Messages: 155

    ditto, this is what i thought first.
    I would get the book for our truck and adjust the shift cable properly.
     
  7. duramax-king

    duramax-king Senior Member
    Messages: 134

    the transmission shifts into all gears.it just won't let me go over 98km/h, if i try going faster it just drops a gear and then goes back up and speed doesn't increase.
     
  8. no lead

    no lead PlowSite.com Addict
    Messages: 1,308

    has it ever gone more than 98 since you bought it? or were you told that is why you needed a trans cable? maybe a throttle cable issue? ever change the fuel filter?
     
  9. CT-TILEMAN

    CT-TILEMAN Member
    Messages: 61

    Did not see it was KPH and not MPH, I know the USA trucks from GM are all limited to either 96 or 98 MPH.

    Hope you get it figured out.
     
  10. duramax-king

    duramax-king Senior Member
    Messages: 134

    no it never went over 98 km/h, and i was told it need a trans cable so i changed it, still won't go ofer 98.could be the throttle cable, will also try changing the fuel filter.
     
  11. dheavychevy38

    dheavychevy38 Senior Member
    Messages: 283

    x2 on the rpm what are they ? What gear ratio does it have ? I had a similar problem with mine and it was a trans issue but the rpms where through the roof.
     
  12. hydro_37

    hydro_37 PlowSite Veteran
    from iowa
    Messages: 3,790

    RPM's and gear ratio would help figure it out more
     
  13. adksnowo

    adksnowo Senior Member
    Messages: 370

    Is the turbo spooling up? Maybe there is no boost? Leaking fuel lines or fuel pump shot (not enough fuel pressure)? Exhaust or turbo ducts leaking?
     
  14. duramax-king

    duramax-king Senior Member
    Messages: 134

    rpms are close to 2700-2800, and everything else is good, i think that someone might have put a speed limiter on it (the previous owner). does anyone know how i can get the limiter off?or check if there is one?gear ratio is 3.73, i think but i'm not quite sure?
     
  15. NICHOLS LANDSCA

    NICHOLS LANDSCA PlowSite Veteran
    Messages: 4,310

    Is there a check engine light? Does it pull up to 60 and then fall on it's nose? Need more info than it just won't go 60. BTW there isn't a throttle cable.
     
  16. duramax-king

    duramax-king Senior Member
    Messages: 134

    no check engine light on, it goes to 60 then if you want to go faster it just won't go.the truck drive normally until around 60mph and then when you go to speed up it shifts down and then a moment later it shifts back up.
     
  17. drp

    drp Senior Member
    from ontario
    Messages: 170

    The RPM is way to high for 3.73 gears at 98km/hr.

    Ford 2004 6.0 auto 3.73 gears 98 km/hr = 1750 rpm

    yours sound way to high.
     
  18. VPRacing

    VPRacing Member
    Messages: 74

    Sounds like the 1st/2nd shift solenoid keeps turning off not allowing the transmission to shift into overdrive... Probably going to need to take it in unless you're a decent mechanic and know about automatic transmissions.

    There are 2 solenoids: 1st to 2nd shift solenoid and 2nd to 3rd shift solenoid.

    1st gear - 1-2 shift solenoid is ON, 2-3 shift solenoid is OFF
    2nd gear - 1-2 shift solenoid is OFF, 2-3 shift solenoid is OFF
    3rd gear - 1-2 shift solenoid is OFF, 2-3 shift solenoid is ON
    4th gear - 1-2 shift solenoid is ON, 2-3 shift solenoid is ON

    In case you want to try to tackle this yourself, I'd start there...

    This is all in regards to the shift linkages being correct and not bent.
     
  19. duramax-king

    duramax-king Senior Member
    Messages: 134

    ok so i went to my mechanic finally and he told me the gears are to low...? does anyone know what gears were availble in those years? or how to check your gears?
     
  20. Plowtoy

    Plowtoy Senior Member
    Messages: 929

    I would suggest going to a dealer and have them run the V.I.N. They would be able to tell you the ratio from that. Also it should be a 4l80e trans behind the 6.5, I don't think there's a shift cable either since the throttle is "fly by wire" and the computer controls the trans. Good luck