GMC losing power

Discussion in 'Shop Talk' started by Rob30, Mar 26, 2006.

  1. Rob30

    Rob30 Well-Known Member Supporter

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    I have an 96 GMC with a 5.7l auto. When hwy driving if I kick into passing gear my amps start droping quickly, the headlights dim, the gauge can get down to 8-9 amps if it stays in passing gear long enough. The truck runs fine otherwise other then hard starting in the morning at times.
    I don't think its the alternater because the the truck charges fine runs around 14 amps when driving.
    Is there somthing in the tranny that wound suck amps in passing gear? Maybe something in the ignition when the engine revs up that high.
    Anyone else have the same problem? Any ideas?
     
  2. idahodave

    idahodave Well-Known Member

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    Fan belt slipping at high RPM
     

  3. dodgetkboy78

    dodgetkboy78 Active Member

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    Sounds like it.
    You may want to look at the tensioner, and see if it is froze up. It might be the alternator too, when you are on the gas, they use more power to run. But it does sound like a belt slipping.
     
  4. Beeman

    Beeman Well-Known Member

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    Your gauge on the dash is a voltage gauge not an amperage gauge. I agree with the others that you most likely have a slipping belt due to wrong/improper belt or misrouted belt and or a bad tensioner.
     
  5. Rob30

    Rob30 Well-Known Member Supporter

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    It has been squeeling a bit at high speeds.
     
  6. idahodave

    idahodave Well-Known Member

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    If the lights dim that fast, your battery is on it's last legs
     
  7. Rob30

    Rob30 Well-Known Member Supporter

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    I haven't fixed it yet but after playing with the ideler pully and spraying om some lube it is keeping the belt tighter. I will be changing the batery soon. Thats probably is why I have had a hard time starting it some mornings.