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Thread: 4L60 to 6L80 Swap

  1. #1
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    4L60 to 6L80 Swap

    Has anybody done a transmission swap from a 4L60 to 6L80 on a Gen IV truck?

  2. #2
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    I have seriously thought the process over a few times. Would need the trans controller harness custom modified (6L80 controller is in the trans) and you would need the shifter from a 6L80 truck. Not sure how the gear shift indicator would work out...if you ahve the digital one it may work ok but if you have the lights on the speedo then it may be a little whacky.

  3. #3
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    I did in my Z

  4. #4
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    He was meaning the 6L not the 4L, Mike.
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  5. #5
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    if you head over to performancetrucks.net and do a search, there are some guys that have done it. One person put it in an older GMT800 and got it to work but had to piggyback ecms for cruise and other functions etc. One other person says he did it but was very cryptic with descriptions so not sure on that one. Also I think speartech (??) swapped a 6l80 into an older truck with good success, but they have good resources.

    All had some issues though. I looked at this pretty close for a while, its doable for sure but there are two styles of fuel systems (one has a fuel module and one does not-there is a discussion of that as well) and the 6L80 wants the module so if that isn't there could be issues....the biggest issue I had was how would the thing read out in the dash and would that cause BCM issues (esp since the only people who can mess with the BCM right now is GM and they weren't interested in helping me out)

    Also, looking at 6.2L with 6L80 swap, by the time you buy engine/tranny, mod the crossmember, driveshaft, mod the wiring, programming, possible dash swap and shifter handle it gets pretty pricey. Now that the the 6L80 is getting more common in the extended cabs and crew cabs I am thinking it will become easier to swap over if you can find a wrecked truck...that way you have all the parts that just drop in.

    Later in 2009 supposedly the 6 speed will come in across the entire line including reg cabs (with current state of disaster though all bets are off)....that might be the way to go as all the ugly stuff is done and just need to drop in the engine of your choice...I guess it depends what kind of deal/trade in a guy can swing on his current truck, might end up cheaper than doing it yourself and certainly easier.

    I would love to pull the 5.3 out of a new RCSB 6 speed Sierra and drop in a modded 6.2L, the thing would still look stock and go like stink...bet even GM service wouldn't notice...be a lot of fun!!
    Last edited by Penguin; 03-04-2009 at 02:29 AM.
    2007 Sierra RCSB 5.3 (for now)

  6. #6
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    Quote Originally Posted by BBA View Post
    I have seriously thought the process over a few times. Would need the trans controller harness custom modified (6L80 controller is in the trans) and you would need the shifter from a 6L80 truck. Not sure how the gear shift indicator would work out...if you ahve the digital one it may work ok but if you have the lights on the speedo then it may be a little whacky.

    you can just get a full engine harness from a denali. the stock shifter and cable works fine.
    2008 GMC Sierra RCSB 4.8L

  7. #7
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    Thanks for the info

  8. #8
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    Quote Originally Posted by RCSBcolo View Post
    you can just get a full engine harness from a denali. The stock shifter and cable works fine.
    Ok but what about the readout on the dash? Obviously can't use Denali dash as don't have top level cluster plus its programmed for 4 speed? I recall there were issues with this.
    2007 Sierra RCSB 5.3 (for now)