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  1. #1

    Default 2002 Chevy Silverado Transmission Issue

    I have a 2002 Silverado 3/4 ton 6.0 gas club cab with 90,000 miles. The truck
    has been good (other than the piston slap issue) . Recently in the last year, when starting from dead stop, the transmission will slip slightly. It has happened may be 20 times in the last year. I was told by a friend that I should take it to a dealer and they will reprogram transmission as this is problem with this years vehicle. I dont trust dealers and mine has not been back to the dealer since I bought it. I have had trans fluid changed every year and use synthetic. Is this just a quirk of truck or a sign of problems to come?

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  2. #2
    Legend unplugged's Avatar
    Join Date
    Sep 2006
    High Deserts of SoCal


    Electronic transmissions....boone or bane? I love the allison in my 06, but then it hasn't needed any work. The pcm can be reprogrammed for different shift points. Your problem may be that simple. Is your truck throwing any DTC codes?

    From: Motor
    Slip-Sliding Away: Deciphering GM Transmission DTC P1870

    Motor, Jun 2006 by Colonna, Wayne

    The newest transmission technology provides nearly unnoticeable torque converter clutch application. As is often the case, an appreciation of how it works will help you understand why if something goes wrong.
    Diagnostic trouble code P1870 (Transmission Component Slippage) is a General Motors-specific code whose set parameters are determined by transmission type and engine size. The PCM monitors and compares engine speed to vehicle speed after the converter clutch has been commanded ON in either high gear or Overdrive. Should the expected rpm ratio exceed predetermined parameters, DTC 1870 sets. And upon doing so, the PCM elevates the transmission main line pressure and stops converter clutch apply.

    In some instances, the PCM also will inhibit 4th gear and may or may not illuminate the MIL. This really is an added safety strategy, as the PCM had already monitored the upshifts and determined all was well through those ranges. Once the vehicle has made it to a cruise state, the PCM then begins to monitor the vehicle's cruise ratio. If at some point the transmission begins to slip, P1870 sets and line pressure is elevated in an attempt to stop any further slippage and prevent further damage. This would explain why DTC 1870 Ls often accompanied by a complaint of a hard 1-2 upshift.
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  3. #3


    Thanks for the information. I just wanted to have a clue before bringing it in to the dealer. I dont trust the rats. May be I can find a buddy who has the tool to read the code.

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