What Causes Jerking Between 45mph And 60mph In Gmc Sierra 1500 5.7 2WD

Posted in Ignition Systems
  • I bought my 1997 Sierra 1500 5.7 Vortec about 6 months ago. I love the truck and plan on keeping it for a very long time as it looks like new with only 74k original miles on it. HOWEVER, problems started when I noticed the check engine light come on. Took it to the dealership and the code read O2 sensor problems. No big deal right? Well they also found that I was leaking fluid from the intake manifold due to a faulty gasket. Looked it up online and found that this is a common problem. Since I knew this would involve stripping the motor down to the intake manifold I elected to replace all critical parts so I would not have to worry about them for a while (intake manifold gaskets, valve cover gaskets, spider injectors, serpentine belt, O2 sensors, water pump, pcv valve, plugs, wires, distributor, alternator, thermostat). I also had some brake work done (master cylinder etc.) Thinking I was done with major maintenance on the truck for several thousand miles I drove away from the dealership. Then it happened…..and has been happening for 2 days. Between 45 and 60 MPH with no hard or acceleration or braking the truck “jerks” intermitantly almost as if the tranny is slipping, but it seems to be in-between gears. This DID NOT happen before I took it in for service!!! Other than that the truck runs great. It is back at the dealership and they are currently at a loss at what it could be. My online research suggest anything from faulty or mis-adjusted brake light switch, faulty spider injector, to torque converter. Please send your thoughts/ suggestions to help stop the bleeding at the dealership!!!! Thanks. ZEP

    There are 10 Answers for "What Causes Jerking Between 45mph And 60mph In Gmc Sierra 1500 5.7 2WD"

    1. inda w says:

      its probly the transmission fluid wore out , i’d change that asap to prevent further damge;)

    2. michael o says:

      chevys are common for transmisions going out at 150000miles but check you ujoints if they are bad they cancause jerking

    3. snowy says:

      My Safari van was doing that a few weeks ago – it was the fuel filter. If had never been changed – it may be time to check yours.

    4. lincman90 says:

      Possibly an issue with the torque convertor locking/unlocking. Doubt that it is U joints if it jerks at speed.

    5. phillip b says:

      check transmission fluid level i have that prob w/ my dodge it went away after fluid change and check seal for tore or ripes and if the truck was fine before the service was done then its the dealerships fault

    6. boogie_4wheel says:

      Congrats on your purchase. The intake manifold gasket leaking coolant IS a common problem. Mine started doing it lightly at 110k miles, but still have never pulled the top to replace it, it is minor compared to some. Another common problem is fuel pumps. My uncle had a GM and replaced his 4 times! I did my only replacement (so far) at 133k. Don’t run the truck under 1/4 tank to keep the pump submerged in fuel to help keep it cooled and they should last longer. If/when you do replace the pump, do skimp out on a replacement, buy an AC Delco unit, it may cost more but it will last longer than the other junk.

      Ok, on with your problem. Before reading everything that you had replaced, I was going to say maybe the torque convertor having lockup problems. There are 2 solenoids associated with the TC locking up, ~$50 each and can be replaced with only removing the tranny pan. Is the engine reving up/down during the jerking? Unlock to lock will result in a few hundred RPM difference. The brake pedal switch can also cause the TC to unlock (the same time that the brake lights illuminate). But was the switch touched, shouldn’t have been…
      With 3.73 gears, the TC will lock up at 40mph under a really light load, and is forced locked at 75mph. So as load changes the TC could unlock at anytime between 40-75 (as speed increases load will need to increase). If the TC was slipping, it should throw a code (P1187 if I remember correctly). But if the TC isn’t locking for some stupid reason, it won’t throw a code.

      I doubt that the timing could/would be off far enough to cause issues.

      May have a vacuum leak? More air entering the motor, the O2 sensors will sense a lean condition and put more fuel into the motor, causing you to speed up slightly. Vacuum leak would probably be more constant though.

      Could have a faulty injector. Pull the plugs and compare. They should all look similar. If one plug is way different than the other 7, that could very easily be your problem.

      Good Luck!!!

    7. the pump guy says:

      Vacuum check, all vacuum lines and controls.Sounds like they left off a hose,cracked one, or installed them wrong.Easy mistake on some since in and out are same size in some instances.Then check if all the required wires are all installed and ,correctly.Something is out of place ,
      misplaced or missing correct location or connection problem.Torque converter wiring can also do it.TCC.

    8. Good ol boy says:

      did they check or change your fuel filter and did they check fuel pressure this is a common problem with weak fuel pumps and with bad filters it may not be your tranny.

    9. paul h says:

      TCC (Torque Converter Clutch) solenoid may be going bad…some are switched by a signal from the brake pedal switch too so a bad switch may be causing it to lock/unlock improperly Check trans fluid level as well as pressures if possible….may be due for a flush also.

    10. baldie says:

      sounds like the sensor that operates the lock-up torque converter is going bad.

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