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Thread: Dumb Question: Is soft shifting bad?

  1. #1
    Join Date
    Jan 2011
    Location
    Los Alamos, New Mexico
    Posts
    78
    My Cars
    1988 735i

    Dumb Question: Is soft shifting bad?

    Hello,

    I have been regularly driving my automatic 735i for a few months now, in both city and highway settings. The transmission had "hard shifts," in that it would clunk into gear. I would always feel the first to second, and then the third to fourth would be very violent. Never really felt the second to third. When warm, the clunk between first and second would disappear. I assumed it was because the filter was in need of replacement. The transmission fluid level is fine. I changed the fluid prior to pushing it into regular duty. About a week ago, it shifted hard into second--enough to shake the car-- and then after that it just stopped clunking into gear. It goes into all gears smoothly and drives well. I only feel a slight bump when it shifts into fourth, but that's the way it was a few years ago.

    I know it's dumb to ask, but is there such a thing as shifting too softly? Should I be worried?

  2. #2
    Join Date
    Jul 2007
    Location
    Oldham UK
    Posts
    3,185
    My Cars
    '00 330i Sprt '92 525i
    The trans uses hydraulic pressure to apply the clutch that results in the gear change. Damper pistons in the valve body control how fast that pressure is applied. If the damper is stuck, that gear might be applied too fast. It is like taking your foot off the clutch too fast on a manual - it goes in with a bang. If the car was not driven for some time, it is possible a piston simply got stuck and has now freed off. If it is now engaging gears gently but firmly, there is no slip and the engine does not rev between gears, then I'd suggest that is how it is supposed to be.

  3. #3
    Join Date
    Jan 2011
    Location
    Los Alamos, New Mexico
    Posts
    78
    My Cars
    1988 735i
    That is reassuring. Thank you. The car sat for at least half a year, and I'm not sure it was well maintained for the last couple years. I have not noticed any slipping, and I've driven it a couple hundred miles since the transmission stopped clunking. It was just alarming for the car to heal itself without explanation.

  4. #4
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,655
    My Cars
    11/88 E32 750iL+98 E36M3
    this is just for info about some email exchanges, problems and ideas, maybe it helps someone in the future:
    Hello Shogun, I desperately need Your help, I hope You can help me.I have 1989 E32 750i. Since I bought it 2 years ago I have some transmission issues. Actually one issue-- hard shifts.. shifts hard when hot. So here is description:
    When everything is cold I have beautiful shifts, sometimes I almost can't feel the shift from 1st to 2nd but after only a few kilometers the shifts get harder and harder. Keep in mind other than hard shifts my transmission works good.. no slip no shift delay.
    So when it is hot it shifts hard 1st 2nd 3rd.. from 3rd to 4th shifts good.. also shifts hard from N to D and I also get hard disengage from D to N.. Somehow from N to R shift is ok. I have read pages and pages of forums and websites, and after a few oil changes (i was not able to do a transmission flush so i did fluid change and filter a couple of times) the problem is still there. After that I decided to drop a valve body and do a rebuild, ordered new valve body gasket, cleaned everything with brake cleaner every spring, valve and channel. the thing was shining like brand new.. after assembly and test drive I was disappointed, the trans shifted same as before! no change. After I did a first oil change there were no big metal parts on magnets it all seemed like normal wear. I also checked the solenoids (I have 4 solenoid version) measured internal resistance and according to manual it was good.. only thing that was of is speed sensor, but i read somewhere that it is temperature dependent and probably has no influence on hard shifts ?!
    Keep in mind the shifts are not neck breaking but definitely not how they should be.. they take a lot of comfort out of my 750.I sometimes hear alternator belt squeak on shifts, so that is definitely a hard shifting. I'm starting to think that it has something to do with oil pressure.. . Let's say I'm driving and everything is up to temperature it is shifting hard, and I make a stop. Turn the car of for a few minutes, start it again.. but after the restart the trans shifts even harder for next 3-4 kilometers and after that goes back to "normal" hard shift. I tried hard reset procedure on car with no change. What do You think? is my torque converter bad? worn clutches? do I have to do a complete trans rebuild? Is it possible that my pressure regulator solenoid is bad even if the internal resistance is within specs. Is it possible that solenoid is causing hard shift? After disassembly of valve body I have not found too much dirt at all and no broken springs or other parts, everything seemed fine. So I have rebuild valve body, new oil and new filter and still have hard shifts.. Please help! Only thing that got a little better after rebuild are downshifts. One thing I want to try. On pressure regulator solenoid body there is adjustable screw. On Japanese website http://e32b12.blogspot.com/search/label/4HP24 I saw that they did some adjusting with that screw and got rid of hard shifts (according to google translate). But I don't know if I should turn the screw clockwise or counter clockwise half a turn or even a complete turn? Looking forward to Your reply
    ------------------
    I will ask some experienced transmission experts to chime in. When we did that on the japanese transmission with the screw on the pressure valve, that was very time comsuming, always had to drain the ATF, remove then pan and adjust 1/4 more or less till it was o.k. Did you already clean the metal screen in front of the pressure valve? https://www.bimmerforums.com/forum/s...hifting-solved
    also maybe you try flushing https://www.bimmerforums.com/forum/s...ns-flush-setup
    -----------------
    Thank You for your reply. Almost all of the fluid in trans is new. From the last rebuild a lot of old fluid came out and after assembly I filled new fluid. The solenoid is some kind of version without metal screen. I have really ran out of options. Maybe the last option is with screw adjusting. I know it will take me a lot of time.. But what should i do.. Do You think that faulty speed sensor can make these problems?
    -------------------
    yes, test the speed sensor, all test data here, 11.5 MB for download http://parts-at.ru/wp-content/upload...Tech-Guide.pdf
    -------------------
    Sir, I know what he says and wants to know. they have three kinds of problem things for control of shifting work.
    1st, not same all time oil running speed.

    transmission oil changing moving speed cold and warm, cold slowly moving hot time fast moving inside of valvebody. this mean change moving speed process any cylinder and piston, any hot time moving fast then shift feel much quickly.
    cold time not fast moving speed then mild shift sometime. if use better or expensive oil, a little bit change those thing. but very little bit.

    2nd, clutch gap not as same as new transmission.

    some car running many years and many miles, so transmission clutch gap is more bigger than original new one. if the gap is too large, valve body have to work more fitting for that, needs more time. if need more 1 second
    that will change engine speed and car running speed, so shift point will change more than original.

    all cars with bad shift not going to lower speed level more than original, they all upper speed change on 1st to 2nd, this reason coming by big clutch gap.

    3rd, piston and cylinder not smooth (most big problem).

    all shift work producing valvebody piston and cylinder. some part not smooth like new unit, because they work everyday, then some cylinder got damage by sliding piston. of course they fill oil all time but when running time oil getting many bubble inside valvebody in hot time. sometime piston side direction touch face to face with valvebody then not smooth.

    when T....san tried to super smooth rebuilding piston part by engine speciality shop, it changed to much smoother shifting work. but very expensive tuning each piston build.

    in my case I always do special coating on cylinder and piston for overhaul valvebody, it is something like engine cylinder coat. I bought them from Sumitomo ceramical company based on molybdenum.
    anyway, all unit not same. one by one to be tried to tuning.

    finaly RELIEF VALVE turn the screw clockwise to more high pressure , anticlockwise to more low pressure. but think about it that is only for relief oil function not change pressure, oil coming enough volume any time minimum engine speed. if coming high rotation, engine speed just relief extra oil not use for valvebody that's all.

    if the leaking oil from oil pump then less oil power for low speed drive, in that case maybe better change relief valve tune, other things not much change.
    -----------------------
    Hi shogun, I have to agree with your comment about adjusting the pressure relief valve. I can only guess you had a pressure gauge testing line pressure and adjusted the valve a little each time? That must have taken hours. A lot of the gearboxes don’t even have the tapping and you have to drill it first. Your friend’s comments are very interesting indeed. I know that the gearbox can compensate for worn clutches and imagined it worked in a similar way to hydraulic brakes. It must be a little more complicated than that. The older 4 speed gearboxes do not have ‘overlap’ shifting where one clutch releases at the same rate as the next gear engages. So I think E...’s problem may be the damper pistons as I wrote in this thread. Unfortunately, we can’t get around the fact that these gearboxes are 30 years old.
    Last edited by shogun; 12-05-2018 at 12:16 AM.
    Shogun tricks and tips for the E32 series are HERE!

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