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Thread: Transmission Slippage?

  1. #1
    Join Date
    Apr 2017
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    San Diego, CA
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    232
    My Cars
    90' 735iL, 90' 535i, 93'

    Transmission Slippage?

    After the months long debacle of hunting down a kinked IACV it's time for an easy fix.

    This one seems pretty straightforward. I'd say that 20% off the time the vehicle shifts hard when accelerating from a complete stop and never at any other time. If I change the gear selection from "A" to "M" then the problem is non-existent although the vehicle will accelerate sluggishly (as it should).

    There is also the occasional "trans program error" which can be bypassed by restarting the vehicle. Though I've heard that can be an electrical issue and it has only happened once since I replaced the main engine ground. It was toast.

    I also know that "M" mode is meant for slippery roads but I'm curious as to why the issue disappears while using it. Other than that the vehicle runs great!

    If anyone has an idea of how I should proceed, your input is invaluable!

  2. #2
    Join Date
    Jan 2005
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    Japan
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    54,654
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    11/88 E32 750iL+98 E36M3
    I have read about some cases on the German forum where a defective throttle valve potentiometer was the problem.
    Did you ever clean the valve body and checked the trans fluid level? Changed the ATF filter?
    Last edited by shogun; 01-22-2019 at 09:02 PM.
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
    Join Date
    Jun 2007
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    Great White North
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    various
    Make model and year of vehicle might help. Lots of trans problems out there.

  4. #4
    Join Date
    Jan 2005
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    11/88 E32 750iL+98 E36M3
    Quote Originally Posted by chazsandiego View Post
    There is also the occasional "trans program error" which can be bypassed by restarting the vehicle. Though I've heard that can be an electrical issue and it has only happened once since I replaced the main engine ground. It was toast. I also know that "M" mode is meant for slippery roads but I'm curious as to why the issue disappears while using it.
    Also clean the switch S-E-M and the shift selector contacts http://www.nmia.com/~dgnrg/page_13.htm
    E34 535 uses electronically controlled ZF transmission - 4HP22EH. The transmission is controlled by the driver through two switches, S/E/M Program Switch and "Shifter Selector" Switch. Both switches are subject to wear and may be desired to be reconditioned thereby avoiding expenses.
    The code plate element provides 7 tracks that are responsible for translation of code to transmission electronics and the speedometer. The wiper provides a bridge for current to traverse from top track to others depending on position of the shifter, so that the code can be established. The contacts of the wiper are connected together. Two bottom contacts are connected separately. The connection between code plate and the wiper is crucial in order for transmission to shift correctly. If bad connection exists, the electronics acquire incorrect code for the position of the shifter and erratic behavior of the transmission results. Use mild sanding paper to clean the tracks of the code plate. The wiper should be re-adjusted by way of gentle pushing away from its frame the connectors to insure good engagement with code plate tracks. Gently push the screw driver perpendicularly to the connectors towards the base of their mounting. The deformation should be substantial enough for the connectors to be able to reach the tracks of the code plate within closed shifter switch body. The pins of the code plate connector are marked in the literature numerically from 1 to 8 with missing "5" for this particular application. Use multimeter to establish connections between pins and tracks. For given position of the shifter the wiper connects tracks with top one directing electricity to connector pins thereby creating a code for transmission electronics.
    The tracks have variable width to insure connection in particular positions. It is important to make sure that besides being able to reach code plate, the wiper has ability to engage precisely the tracks that must be engaged without shorting ones that must not come in contact, particularly the narrow parts of tracks which are only there to carry connections to wide segments. After sanding code plate, displacing the connectors of the wiper away from its frame, and checking that the wiper does not provide undesired connections, the switch is reassembled and is ready for chek-up. Using multimeter to ensure that the connection between pin "1" and other pins necessary for given position exists and those not necessary for given position do not exist (!) one can tell whether the operation is proper. In case some tracks short with wiper connectors, the connector tip balls may have to be filed at the sides to establish clearance. In position "Reverse", for example, the pins that have to show the connection with "1" are "4" and "8". Pins "2" and "3" must not provide connections.
    http://www.bimmerboard.com/forums/posts/744694/
    Shogun tricks and tips for the E32 series are HERE!

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