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Thread: 99 Yukon to LS1 swap Help/ info please

  1. #1
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    99 Yukon to LS1 swap Help/ info please

    I have a complete 99 Trans-Am with a T6 TRANS. I need to know or get any advise on what i'm going to need to do to put the LS1 ENGINE in my 99 yukon 4×4. I have a 5.7 crate engine in the yukon but I believe ill be much happier with the LS1 and I just need to know what modifications i'm facing. And which pcm I should use. Any help would be a blessing.

  2. #2
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    99 yukon as in GMT400 or GMT800?
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  3. #3
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    how do you tell the difference in the two

    forgive my ignorance. But i dont know how to tell the difference between the 2. How

  4. #4
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    considering it has a 5.7 crate engine and he is wanting to swap in a LS1 (5.7) i would have to guess thats its a 400.............
    01 Silverado

  5. #5
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    The yukon has the 5.7 with the distributor. And the ls1 uses individual coils as i'm sure you already know. I've searched the gmt400 on the net and im sure that's what I have.

  6. #6
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    should b gmt400 with the 88 to 98 body style

  7. #7
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    do you have the ls1 harness??? i would think that the motor mounts will work, but im probably wrong, also are you keeping it 4x4???
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    2006 Silverado
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  9. #9
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    Quote Originally Posted by gwsmith34 View Post
    The yukon has the 5.7 with the distributor. And the ls1 uses individual coils as i'm sure you already know. I've searched the gmt400 on the net and im sure that's what I have.
    You have the VIN R 5.7L in there right now. The motor mounts will not bolt up to the LS1. They do make plates that bolt to the LS1 block and allow you to retain your original mounts. What colors are the wire harness plugs that connect to your engine computer (PCM). Your current 4L60E tranny will bolt right up to the LS1. You will need a spacer that is made to go between the rear of the crank and the front of the torque converter. The distance from the end of the crank to the face of the engine bellhousing is like .4" shorter than your vin R 350. I would just use the LS1 flywheel so you can use the starter that comes with it, Otherwise you will need to elongate your flywheel holes for the torque converter holes to line up for its bolts.

  10. #10
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    He wouldnt be able to use the flywheel, because the LS1 is in front of a manual trans. He will want to get a LS1 flexplate though.......

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