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Thread: Leaking neutral safety switch...a simple fix?

  1. #1
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    Leaking neutral safety switch...a simple fix?

    Hi guys,

    Today I noticed a light film of oil on one side of the tranny pan. Turns out that the neutral safety switch seems to be leaking ever so lightly. I have searched this forum for some advice on how to repair/replace that switch.
    Some have repaired the switch by spraying the internals with WD40 and opening it up and resealing it. I have never removed that switch from the passenger side of the tranny case. I know there are 2 10mm bolts that hold it to the tranny case but not sure if I can simply remove those bolts and simply pull the switch out or do I need to drain the fluid and remove the pan and/or valve body to remove the switch.
    My car starts and runs fine...other than an a rare sudden up/down shift that occurs at low speeds. My main reason is to prevent the leak of fluid.
    Can someone please let me know if I am on the right track in believing these switches could leak and are easily replaced by removing the 2 bolts?

    As always....thanks for all the great advice.

  2. #2
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    Look at the level of the fill plug. The cold not running level is well above the fill hole. If the sensor isn't above that you will get oil when removed.

  3. #3
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    Hi Steve
    thanks for advice
    would you know if this switch simply pulls out after removing the 2 10 mm bolts or if some other parts need to be removed as well?
    if this switch simply pops into the tranny case there must be an o ring or some sort of gasket to prevent fluid leaks

  4. #4
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    Sorry, I just changed my fluid but I didn't pay attention to that part. I took a look at realoem but I can't identify what part you're talking about, can you?
    http://www.realoem.com/bmw/enUS/part...MW-750iL&mg=24
    Last edited by COSteve; 05-19-2019 at 12:32 AM.

  5. #5
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    Hi Steve..thanks for the reply. Yes I was able to locate the part under realoem under individual trans parts. its part number 8 position switch...part number 24101423763

    I believe there is a shaft that the switch connects to and the leak could be at the shaft and it makes it appear that fluid is leaking from the switch. I have not removed the switch from the transmission case and believe the shaft that rotates as we shift the gear selector may have o-rings or some other gasket that keeps the fluid from leaking.
    I have never removed this type of switch but it appears to be externally mounted to the transmission by 2 10 mm bolts...so I dont believe it should have any exposure to tranny fluid. I think the gear selector shaft protrudes from the trans case and that is where the leak is happening. oddly enough, on the opposite side of the transmission case (driverside) where the cable from the gear selector enters the transmission...there is no wetness. So I believe the o ring or gasket is fine on that side but the passenger side where the neutral safety switch is may have a worn out o ring. This is only my guess and I was hoping someone on the forum would be able to confirm before I replace the switch that may be working just fine.

    Thanks again for your help

  6. #6
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    Part number 7 is shown as shaft seal. That would be a place to start. The switch assembly looks to be quite expensive.

  7. #7
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    Yeah...I intend to research whether its a shaft seal leaking since it would not make sense for a plastic neutral safety switch to be exposed to hot trans fluid...so I believe the shaft that connects to the gear selector cable on the drivers side of the transmission needs to be removed and the entire shaft might need to be removed in order to replace what I believe are two orings on either side of it?? I am totally guessing here and not sure if that is the problem..the switch is VERY expensive and seems to be working fine..I just want to stop the slow leak that appears to be happening in that area of the transmission. I hope some one that has gone through this procedure chimes in with some advice.

  8. #8
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    I have a whole thread on this on here. Is it the selector switch you are talking about?

    There is a seal behind it that gets hard and needs to be replaced. It will not gush fluid out while you are replacing it, but it is very hard to do under the car to pry that thing out without scoring the transmission. The seal itself is like $3
    1998 740il | 9/97 build | 233k | schwarz 2 | sandbeige
    mods: m-pars | Bilsteins & B&G springs | suede headliner | Arduino w/ custom I-bus coding | Android HDMI on nav | ValentineOne | StealthOne | llumar ceramic tint | bmw aux w/ 2A usb charging
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  9. #9
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    Hi Racer...thanks for the info
    Yes i noticed a slight wetness on the passenger side of the trans pan and not on the drivers side where the gear selector enters the transmission.
    Can you verify that the shaft goes through the entire case and has seals on both ends? I have never removed the neutral safety switch or the gear selector shaft so I'm not certain what to expect.
    I have priced out the seals and saw prices from $6 for Corteco to $20 from BMW.
    Thanks again for your help...this forum is a life saver

  10. #10
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    The selector switch will come off on the side and expose the seal you need to replace. Pry it out and EVENLY press in the new one without it catching and tearing (that's the hardest part). Done
    1998 740il | 9/97 build | 233k | schwarz 2 | sandbeige
    mods: m-pars | Bilsteins & B&G springs | suede headliner | Arduino w/ custom I-bus coding | Android HDMI on nav | ValentineOne | StealthOne | llumar ceramic tint | bmw aux w/ 2A usb charging
    retrofits: full nav | MKIV | bluetooth TCU | SES voice recognition | BM53 w/ AUX input | video module w/ AV input | backup cam | I-bus 6 CDC | oem sirius xm | oem xenon | power rear sunshade and side shades | PDC front and rear | rain sensing wipers | BMW DWS tire pressure monitor | interior and exterior lighted door handles | front seat heaters | heated steering wheel | euro rear fog lights | ski pass with non-ski pass arm rest | folding mirrors

  11. #11
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    Now thats the kind of news I was looking forward to...nice and easy...thanks alot.
    I may as well change the oring on the opposite side where the gear selector enters the trans case...even though it doesnt seem to be leaking yet. Kinda makes sense to attack it while im down there
    Thanks again racer

  12. #12
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    It does not go through the driver's side. The selector switch moves an arm, which slides a piston in the valve body to change where the fluid goes. There is nothing on the driver's side to worry about.

    I make it sound easy, because there are not many steps, but it is NOT easy. There is little room to work.

    You need a few things on hand for doing this job:

    An assortment of picks and things to pry with tips at various angles (Harbor Freight has a large kit with some that are very thick and heavy duty, which you will need)
    Multiple seals on hand (it is very easy to have the seal catch the edge of the case or shaft as you are reinstalling, which will tear it. You will then need to pry it out all over again and reinstall a new one.)
    Ramps or some way to get the car up
    You need to remove the transmission mounts and loosen the transmission crossmember in order to drop the transmission down enough to get the switch out
    Gloves and tons of paper towels, since leaked fluid and grease will be everywhere.
    Something soft between your head and the floor.

    here is my thread: https://www.bimmerforums.com/forum/s...tor+shaft+seal

    You can see I had this problem all the way back in 2015 but didn't fix it until this year.
    Last edited by racer2086; 05-20-2019 at 10:30 AM.
    1998 740il | 9/97 build | 233k | schwarz 2 | sandbeige
    mods: m-pars | Bilsteins & B&G springs | suede headliner | Arduino w/ custom I-bus coding | Android HDMI on nav | ValentineOne | StealthOne | llumar ceramic tint | bmw aux w/ 2A usb charging
    retrofits: full nav | MKIV | bluetooth TCU | SES voice recognition | BM53 w/ AUX input | video module w/ AV input | backup cam | I-bus 6 CDC | oem sirius xm | oem xenon | power rear sunshade and side shades | PDC front and rear | rain sensing wipers | BMW DWS tire pressure monitor | interior and exterior lighted door handles | front seat heaters | heated steering wheel | euro rear fog lights | ski pass with non-ski pass arm rest | folding mirrors

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