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Thread: 1991 750IL Transmission issues (guessing that this is the 1000th time its been asked)

  1. #1
    Join Date
    Sep 2018
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    Mid Michigan`
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    1991 750il,

    1991 750IL Transmission issues (guessing that this is the 1000th time its been asked)

    Ok picked up a 91 750IL tranny leaking (more on that in a bit) driving it does not go into 4th gear and reverse is very week initially the battery was bad and replaced it still having issues.

    replaced battery, reverse still runs at less than idle speed my mechanic topped of tranny (there is a leak i have yet to diagnose). still doesn't go into 4th gear mechanic says tranny is fried so I am in a pickle, A can I swap out to a 22(its a 24) easily there are a few in my area that are working and reliable. But before I do that I want to explore all the options to repair mine. I am guessing that I am not the first person to have this issue.

  2. #2
    Join Date
    Jan 2005
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    My Cars
    11/88 E32 750iL+98 E36M3
    Find a shop with a diagnostic tool which can read also transmission faults on these cars, that means a pre-OBD diagnostic tool. A Peake tester is not enough in such a case.
    Pull the plug of the transmission connecting wire cable between transmission control unit and transmission at the side of the transmission. If the plug is inside full of ATF, this could cause contact problems.
    Is the EML light coming on when you switch ignition on and then goes out after 2-3 seconds?
    Because it could also be that the transmission works perfect but the system of the drive line has a problem and then it goes into limpmode.
    There are many parts which work together with the EML system https://www.europeantransmissions.co...MW/EML-BMW.pdf

    If an 4HP22 fits, has to be checked, the bell housing has to be changed in any case, as the 4HP24 bell housing is much larger in diameter, also check if the input shaft of the 4HP24 is larger in dia, as also the torque converter is different.
    The internals of the 4HP24 are enforced compared to the 4HP22
    There are numerous changes between 4HP22 (used in for example E32 735) and 4HP24 (used on E32 750).

    First off

    - Springs with different rates are incorporated

    - the torque converter diameter is increased to 280 mm

    - the bearing surface of the torque converter is longer to take the stronger loads

    - the converter lockup clutch diameter is increased to 300mm

    - the transmission bell housing is larger due to the increased converter size

    - the A tranfer plate is 15 mm wider in order to accept the larger a clutch

    -the stator wheel shaft is now mounted with 6 countersunk screws for a tighter connection with the transfer plate

    - a new pump body was designed for the longer converter shaft bearing

    - the splines on the input shaft are longer

    - both sealing rings on the input shaft are cast iron

    - the A clutch has a larger diameter and the clutch friction surfaces are increased in size also

    - the number of plates in the B,C and D clutches was increased by one inch each

    - the one way clutch for 2nd gear has been stenghtened and riveted together

    - the one-way clutch for 3rd gear was changed from a roller type to a locking body type for greater torque

    - the planetary gear for 4 is much stronger now with forged webs

    - the output shaft diameter is increased and 2 holes are provided for more lubrication

    - the output flange has a larger bolt circle to take more force
    -the pan is deeper

    - the filter is different for the deeper pan = longer neck

    - valve body plates gasket is different

    - Last but not least, remember that early E32 have trannies with 8 pins connector and the other ones with 7 pins. My 11/88 750 has 8 pins.
    Last edited by shogun; 10-03-2018 at 07:01 PM.
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
    Join Date
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    11/87 735i & 735il P/C
    Quote Originally Posted by sutterkane66 View Post
    my mechanic topped of tranny (there is a leak i have yet to diagnose)
    Is your mechanic experienced with these cars???

    Getting the fluid level right in these cars is a delicate procedure. The tranny must be at full operating temp (like after 10-15 miles on the highway), the engine running, and in park or neutral on a level surface. If that procedure wasn't followed, then I'd bet the tranny is overfilled.

    Might not be the source of your probs, but definitely something to keep in mind.
    1983 4-spd Mercedes 240d w/403k - Sold!

    11/87 E32 735iA w/45k - Daily Driver (finally!)

    04/88 E32 735iL - Parts Car

  4. #4
    Join Date
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    11/88 E32 750iL+98 E36M3
    If you have much time, read this thread with a problem with a 4HP24, even the wiring and remake of the wire loom between TCU and trans was discussed in detail, and also the TCU was repaired https://www.bimmerforums.com/forum/s...mission-Issues
    not always the transmission hardware is the problem.
    Shogun tricks and tips for the E32 series are HERE!

  5. #5
    Join Date
    Sep 2018
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    Mid Michigan`
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    1991 750il,
    geesh what did I get myself into!!! Thank you all for the feedback. I will start troubleshooting in the next couple days. I can say that I drove it today and it shifts hard but drives strong.

  6. #6
    Join Date
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    11/88 E32 750iL+98 E36M3
    Hard shifting could be too low or too high ATF, or -usually- a dirty valve body, which has to be cleaned and the balls replaced and all solenoids disassembled, polished, tested. There is a DIY on my website for this, but there are also many shops which offer rebuilt valve bodies.

    To buy a 750 is the easiest thing, but then starts the maintenance and repair, most shops do not know the M70 engine and they cannot help much, so you have to depend on the forum and your own skills.
    As Philly Bob once said: "The purchase price is just the beginning. Now you have to repair it if it breaks. These cars are addictive (ask any one of us) but sometimes love hurts! Sooo If you "Ain't Skeered" yet... God Speed and good luck! And welcome to the world of the e32 7's. These cars are like a certain woman I know (who will remain un-named). A true thing of beauty, but very high maintenance and demanding of a lot of attention...
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
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    1991 750il,
    ok I noticed today that if my mirror switch was on passenger side every time I shifted from gear to gear the mirror moved.

  8. #8
    Join Date
    Jan 2005
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    Japan
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    11/88 E32 750iL+98 E36M3
    Shogun tricks and tips for the E32 series are HERE!

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