97 GMC Suburban Not Shifting Into D or 4th On Freeway

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by Tracey121, Jan 19, 2013.

  1. Tracey121

    Tracey121 New Member

    97 GMC C1500 350 Gas
    135000 miles
    New injectors
    New plugs and wires
    All new O2 sensors
    New Catalytic Converter
    Oil and Trans fluid change now due

    Truck has been fairly well maintained with regular fluids, etc.
    Recent smell of trans or pw steering fluid, but no noticeable drops on driveway or loss on dip stick.
    Odor most pronounced after a freeway drive.
    Rpms are way off. Down shifted from D to 3rd today on freeway. No change in RPMs at all.
    Rpms are 2200 at 53 and 2500 at 60, but that is normal for 3rd gear.
    Usually, rpms are 2000 at 70mph dead on.

    It seemed that the odor appeared after the recent replacement of converters and O2 sensors by Pepboys. But, not certain.

    Truck seems to be shifting into gear a touch harder than normal with a noticeable thud.

    What would be your best guess as to the cause of the truck not shifting up to 4th at freeway speeds?

    Where should I begin to look?

    Thanks very much,

  2. a.graham52

    a.graham52 Rockstar 100 Posts

    check engine light on?
    also check your trans fluid for proper fluid and not burned.
  3. Tracey121

    Tracey121 New Member


    Yes engine light is on. Fluid is at the bottom of normal level.
    I don't know yet what the engine code is, but I will shortly.
  4. a.graham52

    a.graham52 Rockstar 100 Posts

    That cel could be causing the problem (something's going on and it's putting the vehicle in limp home) or you will have trans codes
  5. TRPLXL2

    TRPLXL2 Epic Member 5+ Years 1000 Posts

    TCC solenoid in the transmission. 97 was the first year that GM used a PWM (pulse width modulation) TCC (torque converter control) solenoid. Basically the ecm sends a signal when the appropriate ranges are met, based on rpms, speed, and throttle position.

    Have it scanned first to see what your code is, but that solenoid is about $20.00 and is easy to change. Since you want to do a fluid change it's the perfect time to do it. You have to drop the transmission pan, let all the fluid drain out. The TCC solenoid is right out in the open, just unplug it from the harness and pull it out of the valve body. Reverse the process.

    Maybe someone else has some other ideas, but the TCC will cause it not to go into 4th gear. There is also the possibility that they damaged the wiring harness going to the transmission while doing the exhaust work, burnt, frayed wires maybe shorting as well. Check wiring under the truck around the transmission.
  6. Tracey121

    Tracey121 New Member


    Thanks for the very extensive reply.
    I will install a new TCC and fluids and see what the code says as well.


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