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Thread: 6l90 swap into 09 Silverado questions

  1. #1
    Potential Tuner
    Join Date
    Jul 2021
    Posts
    5

    6l90 swap into 09 Silverado questions

    Ok so to start the truck is a 2009 Silverado 1500 2wd 4.8l uses e38 ecm t42 Tcm with 4l70
    I recently installed a 6l90 trans from a 2017 express 2500 and changed the tcm to the 08-11 tcm. My mobile flash guy had the rom dump from a 2010 express that he cloned into my tcm. The trans works great after changing shift points and tcc lockup stuff.

    My only problem is that tow haul doesn?t work it turns the light on on the cluster but I don?t think the trans sees the command
    And tap shift don?t work I bought the correct shifter the truck came pre wire for tap shift to the bcm but using a scanner the bcm doesn?t se the command from the tap switch.

    I am thinking that since the truck didn?t come with tap shift that it is not enabled in bcm but that is not my cup of tea

    Is there anyone on here that has experience with this swap or now?s how to make tow haul and tap shift work like factory

    I don?t really won?t to have to use a different set of switches mounted somewhere else I would like to use the factory parts.

    Any input is appreciated
    And sorry no tune files I don?t have my laptop with me right now.

    Also the tcm has a different vin in it than any other module in the truck I?m not sure if that really matters but just letting you know.

  2. #2
    Potential Tuner
    Join Date
    Apr 2024
    Posts
    3
    Talk to your tuner. There is the ability to tune multiple trans tables, but a lot of tuners just use 1 since it should be optimized.

    Is that TCM capable of tapshift? I don't remember it in the older trucks, but I didn't drive a lot of them. Lots of 07 classic and older and 13 and newer.