4L60e Harsh shift?

Discussion in 'Transmission Forum' started by buzzstpoint, Mar 15, 2012.

  1. buzzstpoint

    buzzstpoint Hero Member

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    1998 GMC Sonoma 2wd 4cylinder
    4L60E transmission.

    I just got this truck not to long ago. I notice when shifting from 1-2 the shift is hard/harsh. Not like it's slamming into gear.
    Any ideas? Shift solenoid? 1-2 accumulator?
     
  2. billr

    billr wrench

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    No trouble codes, and the CEL does work? That hard 1-2 is the prime symptom when P1870 is set. P1870 means internal slippage has been detected, so the trans defaults to full hydraulic pressure trying to keep slippage (and damage to the trans) at a minimum. That full pressure causes hard shifts, with 1-2 being most noticeable. If it is P1870, then clear the code, it may not come back for a long time. And add some LubeGard "Red". That's what the revered Transman suggested to me, and my 4L60E is still OK after several years and many thousands of miles. I have to reset the P1870 about once a year.
     
  3. buzzstpoint

    buzzstpoint Hero Member

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    Yes, the CEL does work and no trouble codes that I can read.

    My scanner doesn't read transmission codes. Unless it would come up with the standard OBD2 codes.
    All other shifts are nice and smooth.

    Even with heavy acceleration the transmission feels strong with no noticeable slippage.
     
  4. billr

    billr wrench

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    In my experience the P1870 will set the CEL on, so that may not be it. However, if there is any question about whether you are seeing trans codes, both present and pending, then I would get it scanned with a more capable tool. With the P1870 the other shifts won't seem hard because of less mechanical gear-reduction and more vehicle speed; and slippage may be even less, that's the purpose of defaulting the hydraulic pressure to "full high".
     
  5. 1983FJ60

    1983FJ60 Full Member

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    A 1998 WOULD SHOW CODES UNDER OBD2 SO I AM GOING TO SAY YOU HAVE A BROKEN 1-2 ACC SPRING THIS IS THE ALUMINUM HOUSING AT THE REAR OF THE VALVEBODY HED ON BY 3 10MM HEAD M6 bolts (sorry caps) make sure to check the bore for scoring as well as check for pin wear in the inner bore if the piston is plastic THROW IT AWAY and use a aluminium piston they are only a few bucks from websites like transpartsusa change your filter and pan gasket at the same time enjoy....
     
  6. jasonn20

    jasonn20 Hero Member

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    How is the engine performing because the PCM calculates line pressure from the TPS and few other engine mounted sensors?
     
  7. VegasGMC

    VegasGMC Jr. Member

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    My '93 Jimmy with same transmission had the same issue since new. At 22k mikes I swapped the trans fluid with Maaco synthetic and the harsh 1-2 shift went away after a few days.
     

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