Torque converter lockup, 05 yukon xl

Discussion in 'GM Powertrain' started by Pikey, Nov 13, 2013.

  1. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    I am curious how I can tell if my converter is locking up on the freeway. My freeway mpg has recently decreased to less than my city mpg. I think that I can feel it locking (which I know is not normal) When I get on the freeway, accelerate slowly to 68mph, I feel an "extra shift" or bump at about 50-55mph. ( I really have to concentrate to notice it) I am just wondering if it is not locking and destroying my mpg. The truck runs great on the freeway, just decreased mpg.
  2. TRPLXL2

    TRPLXL2 Epic Member 5+ Years 1000 Posts

    If you have a scanner that can read transmission data that's how I do it, I leave the scanner plugged in and drive and watch the t/c lockup status. It will say open or closed.
  3. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Sorry Mike, I missed this earlier. You should be able to tell watching the tach. If the tach rpms change very little when you push the pedal around 65, the TC is locked (and engine rpm is tied to rear axle/wheel speed). If the engine speeds up easily, the TC is not locked.
  4. buckmeister2

    buckmeister2 Rockstar 4 Years 100 Posts

    If you accelerate slowly, you can feel the lockup, and that is normal. The reason your mileage has dropped is due to the oxygenation of fuel in your area, which generally begins around Nov. 1, and ends around May 1. It will cost you 1-2 MPG, and there is not a thing you can do about it, except to thank your liberal environmentalist politicians who know virtually nothing about vehicles.

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