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4t65e final drive and swap questions

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  • 4t65e final drive and swap questions

    So i have a 2002 olds intrigue. I know, i know the 3.5 is technically a 90deg v6, but my question is about transmissions.
    So I'm slipping in 3rd gear right now. I found a 4t65e for $240 with 90,000 miles but it's from a 2008 impala. I have figured out how to re pin the electrical connector to make it work. My question is about the final drive ratio. I'm having trouble finding the info I need on this specific trans code. It's labeled as a 8ASB.
    As i can figure it that makes it a M15 with a 245mm torque convertor and a final drive ratio of 2.86:1 or 3.05:1 but i can't figure out which. I really need it to be a 3.05 so i don't screw up the pcm in the olds and get into some kind of limp mode. And if it is a 2.86 is the difference in the sprocket set or dif, or both? Basically what would i have to scavenge off my old trans to get to the ratio i need?
    Any input is welcomed here guys (or gals)

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    Last edited by albfink; 05-22-2016, 02:54 PM.

  • #2
    Ok, so I'm going to answer my own question here in case anyone else has the same issue in the future.
    First, I found this website
    Which says the overall final drive in an impala with a 3.5L sfi is 2.86:1
    Second i went a different route because i didn't want to believe this. Rock auto sells a reman trans for a 2008 impala that they say matches codes 6ASB, 7ASB, 8ASB, and 6PAB. I found nothing on any of these but i did find info on a 4PAB on this site under 2004 model year, which is likely the same.
    It says the drive/driven sprocket is 35/35 and the differential ratio is 2.86:1, for an overall ratio of 2.86:1.
    Also, i cross referenced the drive and driven sprockets sold for a 2008 impala on rock auto and they were both 35 tooth.
    This tells me that the 8ASB trans, in all likelihood is 35/35 drive/driven sprocket with a 2.86 differential. I know what i have in my olds is a 35/35 with a 3.05 differential. So I'm just going to change the differentials between them and go.
    Sorry if this is confusing but it was for me too. If you don't understand the drive/driven situation a little research will she'd light on the matter.
    Please let me know if my thinking is flawed.

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    Last edited by albfink; 05-24-2016, 08:18 PM.


    • #3
      Quick update. I did the trans swap this weekend, and it was a bear. I ended up swapping the diffs between the transmissions, which i did not realise would come out with the driven shaft attached haha. But it all worked out ok. Other than that it was just moving 3 wires and adding a ground in the electrical connector and i now have 2008 4t65e in a 2002 oldsmobile.

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