99 yukon shifts hard 1st to 2nd

Discussion in 'GM Powertrain' started by mrpyromaniac, Mar 10, 2009.

  1. mrpyromaniac

    mrpyromaniac New Member

    I have a 99 Yukon, around 133k, just replaced the ujoints. The truck still shifts hard between first and second gear, sometimes hard, sometimes not bad at all. Trans fluid is fine, when I changed the ujoints, I discovered some play in the transfer case when turning each axle. A slight clicking sound like there was play in the gears. Would this cause the truck to shift hard between 1st and 2nd or is something else a problem? Thanks...
  2. mjalstad

    mjalstad Rockstar 100 Posts

    Get it scanned for codes. A lot of transmission codes will not make your check engine light come on. My truck shifts really hard and I never knew why until I decided to check for codes even though my check engine light wasn't on. I ended up finding a P0748 I think which was PC Solenoid circuit. Because the PC Solenoid is not working, the computer automatically demands maximum line pressure which is causing my hard shifts.
  3. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    Yes many codes never turn on the Check Engine Light. Don't drive your truck too long without fixing the code or the high line pressure can cause your sun-shell to break. Once this happens you will have no reverse and no 4th gear.
  4. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    When was the tranny last serviced? Might be something that simple.

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