4T80E 3.11 to 3.71 swap - Page 3
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Northstar Engines and System Technical Discussion Discussion, 4T80E 3.11 to 3.71 swap in Cadillac Engine Technical Discussion; Gears...
  1. #31
    AJxtcman's Avatar
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    Re: 4T80E 3.11 to 3.71 swap

    Gears
    Attached Images

  2. #32
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    Re: 4T80E 3.11 to 3.71 swap

    85° outside and I left the AIR ON.
    I can't believe I left the AIR ON
    14.61 @ 103.5
    Attached Images

  3. #33
    Highline Cady's Avatar
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    Re: 4T80E 3.11 to 3.71 swap

    AJ, I'm loving the new gears. Great work!!! Thanks again.

  4. #34
    Highline Cady's Avatar
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    Re: 4T80E 3.11 to 3.71 swap

    Oh ya and thanx for posting the pictures.

  5. #35
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    Re: 4T80E 3.11 to 3.71 swap

    Nice time. The car should have a WOT A/C cutout so it shouldn't matter if the A/C was on or not.

    Highline, need more feedback! Better throttle response? Faster acceleration? Feels like another 100 horse? Details!

  6. #36
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    Re: 4T80E 3.11 to 3.71 swap

    Quote Originally Posted by jadcock View Post
    Nice time. The car should have a WOT A/C cutout so it shouldn't matter if the A/C was on or not.

    Highline, need more feedback! Better throttle response? Faster acceleration? Feels like another 100 horse? Details!
    Close, but not quite. Yes the AC kick out at WOT, but how long does it need to see WOT before it releases the relay? How long does it take for the clutch to release?
    1/2 second of lower power?
    1/4 second before you get full power?
    .
    Jadcock Thank for your input from the beginning I am glad you pointed out the GXP. That has real been a big help in shutting people up at the dealership. Thanks again.

  7. #37
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    Re: 4T80E 3.11 to 3.71 swap

    I was in to it all of 2 hours.

  8. #38
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    Re: 4T80E 3.11 to 3.71 swap

    Quote Originally Posted by AJxtcman View Post
    Jadcock Thank for your input from the beginning I am glad you pointed out the GXP. That has real been a big help in shutting people up at the dealership. Thanks again.
    If I still had my '97 SLS, and you could tune out the difference in final drive ratio to make the PCM happy, I'd have you swap the gears. I agree that it's the best modification you can do to a LD8/3.11 car.

    My brother owns my old '97 SLS now, maybe I'll mention this to him.

  9. #39
    Highline Cady's Avatar
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    Re: 4T80E 3.11 to 3.71 swap

    Jadcock, sorry I've been out running around. To answer some of your questions, yes I think it has better throttle response, and yes the acceleration is better, no I don't think it added 100 horses. They are the same gears that you have in your STS. First the very little paperwork I can find on a factory stock DHS show 1/4 mile times at 16 flat. I know everybody has their opinions on G-Tech, but that G-tech on a hot humid day showed a 15.09 1/4 with the stock (3.11) gears and AJ's tune and exhaust and Volant intake. After the 3.71's were installed the very same G-tech showed a 14.61 on another hot humid day all other modifications were the same and the car had a full tank of gas.

    So, no matter what your opinion of G-tech, there was a significant improvement. Now for all the years I'ved owned it with the 3.11's I personally feel a noticeable difference the last couple days with the 3.71's. AJ tuned it originally with the 3.11's and it would shift from second to third at 96 mph, with the 3.71's it shifts from second to third at about 83mph (I also have 17" STS wheels). So basically what I have noticed is quicker acceleration and when I'm driving around the car is reved up higher nearer to the torque band, which I like personally, but I'm sure will cost me some MPG's, but I personally don't care about gas mileage.

    I personally think this was a huge change for my car. The gears and AJ's tune have really woken up my N*, bye far worth every penny, in my opinion, and truly that is all that matters to me. The exhaust, I think, did a little and the Volant only added noise (those things are shit for the Deville/DTS in my opinion, I laughed when I pulled it out of the box it was warped and there were huge gaps everywhere, so I modified it to fix all their F***UPS), it sounds great in combination with the exhaust don't get me wrong, but I think the intake may actually hurt performance slightly. Anyway, I was looking forward to getting the Cady down to the dragstrip this weekend but they aren't offering "fun racing" this weekend. They are on Wednesday nite, but I'm still not sure if I'll be able to get down there Wed. It sucks, this weekend would have worked out perfectly.

  10. #40
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    Re: 4T80E 3.11 to 3.71 swap

    Thanks for the review. It sounds like it was worth it.

    I'm sure the G-tech isn't 100% empirically accurate, but I think it's a wonderful tuning tool, assuming you have your technique down and can launch the same every time. Even if it's not accurate to the 10th, as long as it's repeatable, it should be accurate to itself, and (as you say), a half second off the 1/4 mile is a half second off, whether it went from 16.0 to 15.5 or from 15.0 to 14.5.

    Glad this worked out.

  11. #41
    Highline Cady's Avatar
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    Re: 4T80E 3.11 to 3.71 swap

    Ya I'm loving it, I wish I'd have swaped these out years ago!

  12. #42
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    Re: 4T80E 3.11 to 3.71 swap


    William I hope this will help.

  13. #43
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    Re: 4T80E 3.11 to 3.71 swap

    My 02 STS is 3.71 final drive already, right?

  14. #44
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    Re: 4T80E 3.11 to 3.71 swap

    Quote Originally Posted by Shaggy View Post
    My 02 STS is 3.71 final drive already, right?
    Correct.
    You have a W rated tire STS also

  15. #45
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    Re: 4T80E 3.11 to 3.71 swap

    Quote Originally Posted by AJxtcman View Post
    Correct.
    You have a W rated tire STS also
    This is true. My shift points seem to be a lot higher than most of the other people are saying, too. Should I be expecting this with my programming?

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