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  1. #1
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    Member No: 32997 sschaefer is an unknown quantity at this point sschaefer's Avatar
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    Yes | No

    540i transmission temperature

    is anyone (Jim?) aware of a tempertaure gauge that can be added to the automatic transmission of a 540iT? I sometimes pull a small trailer and would be more at ease if I knew when/if the trasnmission were overheating ($7000 to replace!!!). Alternatively, if the answer is no, then will I get a warning light if the temp gets too high???

    thanks in advance - this forum is great!

    Saul
    1999 540iT
    (aka Bella - my wife drives it - I get to drive the IS300!)


  2. #2
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    Member No: 4328 jimlev will become famous soon enough jimlev will become famous soon enough jimlev's Avatar
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    Yes | No

    There are many transmission temp gauges (m)

    available. Here are about 10 pages to choose from.
    I don't have an auto so you will need to find a sensor of the correct thread size to fit into one of the openings in the tranny.
    Someone here that has changed their auto tranny fluid can chime in with a possible sensor location.

    Jim Lev
    2000 540/6
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  3. #3
    Jim Cash
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    Yes | No

    Re: 540i transmission temperature

    The transmission computer already monitors the transmission temperature - there is a sensor built into the internal wiring.

    While you can not monitor the temperature (unless you get a computer and software that does on line monitoring) the transmission will put you into emergency operation mode if the temperature gets too high.

    I know this does not allow you to monitor the changing temperature - but at least it will prevent a transmission failure - the down side would be that you would have to pull over and wait.

    Since some of the heat is caused by constant gear changing I think you would be safer if you get into heavy duty pulling (hilly area) by simply putting it into a lower gear and leaving it there.

    Also - use the cruise control if and when you can - that brings in a special transmission program that decreceses the tendency to change gears - at the expense of not always being in the most responsive gear.

    Cheers
    Jim Cash

  4. #4
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    Inner Circle ©155 since: Jul 21, 2003 edjack will become famous soon enough edjack's Avatar
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    Yes | No

    If you install a temp sensor in the drain plug...

    opening, realize that the lube in the sump is the coolest. The hottest fluid is on its way to the trans cooler.
    Ed in San Jose. BMW CCA member since 1980.

    '97 540i 6 speed. Build Date 3/97. Aspensilber over Aubergine leather.

  5. #5
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    Re: If you install a temp sensor in the drain plug...

    thanks guys - I knew you'd come through. I use the "manual" selector and try to stay in 3rd or 4th on the road, being very gentle on any hills - it's good to know that the tranny will go into safety if it gets too hot, so I'll try that for now. I also change the fluid every 30K.

    Cheers,

    Saul
    1999 540iT no mods 'cept a hitch

  6. #6
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    Re: 540i transmission temp, defective sensor

    I recently once experienced a surprising spurious downshift and had the OBD2 memory checked. They found a transmission temp sensor fault which lead them to unearth a service bulletin from 2001 (#24-02-01) where BMW reports a temperature sensor wire harness crimp issue. Covered under warranty IF spurious upshifts or downshifts are reported by the customer. The repair involves replacing the wire harness for the transmission valve body. Quoted cost: around 850$ !!

    Where things get interesting is that BMW declined coverage of the work & parts under CPO warranty BECAUSE there is a service bulletin. In other words, BMW has a manufacturing defect resulting in failures, they issue a service bulletin, and claim they can waive CPO coverage because of that. Needless to say that I did not find any terms of that nature in the CPO warranty booklet and that I'll escalate this to the dealership manager.


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