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Transmission woes

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Bones, Mar 13, 2003.

  1. Bones

    Bones Newbie

    Mar 12, 2003
    Likes Received:
    I own a 1991 2500 4x4 Suburban. I have a technical question that I hope someone can help me with. The trans in my truck is the mighty 4L80-E. The problem I am having is a really bad TCC shudder and a loss of overdrive(4th gear). It does not happen all the time. I am getting code 68 out of the PCM/TCM. The other day I was cruising at about 75mph on the interstate when suddenly it dropped down to 3rd gear and would not go back into 4th. After shutting it down and letting it sit in a parking lot for about an hour I fired it back up and drove home with no problems. Someone please help. Any info provided would be very appreciated.

  2. Okiemuddog

    Okiemuddog 1/2 ton status

    Mar 3, 2003
    Likes Received:
    Guthrie, Oklahoma
    When was the last time the fluid was changed? My 96 Z-28 with a 4L60E would devolop a shudder under light power when the fluid was getting old. I don't know if changing the fluid would help or hender, some say that changing the fluid will make the problem worse, but if you are loosing O/D then changing the fluid can't hurt anything.

    Just my 2 cents

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