2011 Silverado 4.8 4spd hard 1-2 shift

Discussion in 'GM Powertrain' started by Dave D., Feb 27, 2011.

  1. Dave D.

    Dave D. New Member

    Been loving my truck for about 4 months now. Went from being a smooth shifter to a "kick in the pants" upshift between 1st and 2nd overnight. Everything else seems fine. I disconnected the battery to reset things and its still a harsh 1/2 shift. Tried Tow haul, no change. Truck only has about 8K KM (5K miles). Guess its off to the service department. Everything I read on the net tells me they are gonna say its normal but the rear end and u-joints not likely to last long.
  2. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Sounds like a valve in the valvebody is sticking or a bad solenoid.
  3. Dave D.

    Dave D. New Member

    Took my truck in this morning, their transmission tech took it for a test drive. Of course they were nice about it but mentioned the trailer brake controller and Fog lights I installed as a possible source of the trouble. With the trailer brake controller, GM provides the four wires in a harness and both my braked trailers operate as expected. The other issue is the fog lights I installed. After researching, I tapped a switched sourse for the low current supply of the fog light relay and fuzed it at 3 amps. Everything has been fine for over two months. Attaching a photo of the switch source in case anyone has an opinion. Many of us like to customize our trucks and GM has not done well to id the switched power sources available in the owners manual. With the new common buss comminications it becomes important for manufacturers to provide aux power sources.

    Attached Files:

  4. Dave D.

    Dave D. New Member

    Well I am a bit happier today. After 10 hours of digging, I have finally found a GM produced document that clearly labels the location for aftermarket power connections and it indicates that I indeed plug into the proper location. So now I have ammunition when my truck goes in and GM tries to deny Warranty.

    <<There are two different locations on a truck that power and grounds can be acquired without having to splice or cut into existing wiring. One is the Mid-Bussed Electrical Center (MBEC) and the other is the Underhood Bussed Electrical Center (UBEC).


    The MBEC is located below the instrument panel to the left of the brake pedal.
    The MBEC has 10 positions for connecting electrical connectors. One of these positions is designated for aftermarket utilization.
    Within the connector (fig. 22) there is a fused 30 amp battery feed, a fused 15 amp battery feed, a fused 10 amp Run/Crank feed, a 300 milliamp RAP (Retained Accessory Power) feed and a ground.

    Circuit Description
    Circuit Number
    Fuse Size

    Battery feed
    15 amps

    Not Used


    Battery feed
    30 amps

    Not Used

    Run/Crank feed
    10 amps

    RAP feed
    300 milliamps

    ---------- Post added at 05:35 PM ---------- Previous post was at 05:28 PM ----------

    I used position 7 for my Foglight switch (assessory feed) to run the Foglight Relay. At least now I know where I can connect ground and power for by CB radio. Note that the PINs are from left to right
    7 5 3 1
    8 6 4 2
  5. Dave D.

    Dave D. New Member

    Truck is home and running perfect. Turned out to be an improperly seated X175 pass through connector to internal tranny wiring harness. Now I know how hard it is to disonnect those weatherpack connectors so this could be sloppy assembly. Why would a guy with a family of four buy a regular cab 4x4. I figured out that I could use the family van and the the couple of storms a year, its not likely all four would be together. So I opted to buy the American assembled regular cab over the Mexican assembled extended variant. My final concern is that Onstar emailed be that my transmission was in need of service but no check engine light ever came on. I had to go and buy a newer OBD2 reader with pulled a P0961 selenoid range control trouble. Now that I am cancelling Onstar, looks like I will need to pull monthly diagnostic report incase its something I don't feel in the seat of my pants.
    Last edited: Mar 10, 2011
  6. Taddpole

    Taddpole Member

    Good news for sure, enjoy that new truck.

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