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Thread: Diff swap

  1. #1
    Join Date
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    Diff swap

    I'm seriously contemplating, doing a diff swap in the pig. Does anyone have any first hand experience? Pros and con's? I realize my gas mileage would suffer. I believe mine is currently 3.07. Maybe go to 3.46 or 4.10.

  2. #2
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    Quote Originally Posted by Wagon727 View Post
    I'm seriously contemplating, doing a diff swap in the pig. Does anyone have any first hand experience? Pros and con's? I realize my gas mileage would suffer. I believe mine is currently 3.07. Maybe go to 3.46 or 4.10.
    I just swapped an Auto diff to a manual diff as part of my I6 sedan manual swap. I tried giving my diff away but wasn't able to find any local takers, so i scrapped it.

    Pro's
    several choices will work 3.07, 3.46, 4.0
    Diff's are pretty widely available and no too much $$$
    swap can be done in a few hours
    quicker of the line

    Cons:
    higher RPM at highway speeds
    quick shift points
    decline in mpg? (not sure)

    When I looked at it, my sense was that more than 50% of the people who use an auto diff with a manual regret it sooner or later.
    I like the lower RPMs on the highway.

  3. #3
    JimLev's Avatar
    JimLev is offline Artifically Aspirated Moderator
    Join Date
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    Sundance Mesa, NM
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    00 540/6, '16 Highlander
    I swapped my 2.81 pegleg diff for an M5 3.15 LSD diff about 10 years ago. Love it.
    Slightly less MPG, RPM is 500 higher than the 2.81 diff.
    Quicker acceleration, less downshifting if you want to pass on the highway, just leave it in 6th and step on it.

  4. #4
    Join Date
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    530i, 535i, 325ic
    Auto or manual car? Makes a big difference.
    I'm running a 3.23 in my manual swapped wagon. I like it.

    I also have a 4.10 in perfect condition if you're interested...

  5. #5
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    Manual, with a 3.07 I think. I'm debating whether or not to go with the 3.46 or 4.10

  6. #6
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    2000 528iT
    What about a auto? What would be a good border pro con choice there?

  7. #7
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    I can only find 528s with 4.10s around here. Does the diff have to be out of a 528? Or do 525s and 530s use the same diff's?

  8. #8
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    Quote Originally Posted by Wagon727 View Post
    I can only find 528s with 4.10s around here. Does the diff have to be out of a 528? Or do 525s and 530s use the same diff's?
    You can use any 6 cyl. diff on your 528.

  9. #9
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    Quote Originally Posted by Wagon727 View Post
    I can only find 528s with 4.10s around here. Does the diff have to be out of a 528? Or do 525s and 530s use the same diff's?
    I think it is 00+ 6 cylinder E39 autos that use a 3.46. I've looked into this before, the 3.46 in my 02 525it just emasculates it. What is ok in a 528 sedan is not great in a 528 touring and emphatically not ok in a 525 touring. But I'm not seeing anything in the US between 3.46 and the 4.10 that the early auto cars used. Too much or not enough.
    98 328is
    02 525ita
    80 528i
    81 528ia
    and decades of owning and driving BMWs

  10. #10
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    Quote Originally Posted by Mike WW View Post
    I think it is 00+ 6 cylinder E39 autos that use a 3.46. I've looked into this before, the 3.46 in my 02 525it just emasculates it. What is ok in a 528 sedan is not great in a 528 touring and emphatically not ok in a 525 touring. But I'm not seeing anything in the US between 3.46 and the 4.10 that the early auto cars used. Too much or not enough.
    3.07 is certainly not enough, in the heavier touring. Its an absolute pig from a dead stop. Lol. I'm sure I'd be content w/ the 3.47 gearing, which is harder to find than the 4.10s around here.

  11. #11
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    Location makes a difference obviously, but there ought to be plenty of 3.46s out there, they used them in 00-03, 528, 525 and 530 sedans and tourings with auto trannys.
    98 328is
    02 525ita
    80 528i
    81 528ia
    and decades of owning and driving BMWs

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