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Thread: Driveshaft Balance

  1. #1
    Join Date
    May 2007
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    Minneapolis, MN
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    87 325e e30

    Driveshaft Balance

    Yesterday while installing a LSD I accidentally separated the driveshaft sections (rear stuck to the driveshaft and pulled out), and now it is out of balance (in terms of spline alignment, it is still balanced at some configuration of the splines). I also stripped 2 (of 4) driveshaft to differential bolts (these are pressed in to the driveshaft). Would it be possible for a driveline place to replace these pressed in bolts, and to properly align the shaft if I brought just the shaft in?

    Also, would I be able to just align the driveshaft in it's correct "phase" (only 2 spline alignment possibilities for this phase) and everything would be good? Do driveshafts always get balanced in phase (as in come from a manufacturer in phase)?

    I've definitely researched, but need some more help. Thanks!

    Gophers FTW

  2. #2
    Join Date
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    Bump. I would also like to hear about driveshaft balancing.

  3. #3
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    There should be subtle white dots on the driveshaft to show the approximate alignment. You'll need to align the U-joints "optically" (use your eyes, perhaps on the floor to get a good reference) to get exactly the right spline. Try a spline in either direction to verify.

    I wasn't able to find the white dots on my driveshaft until after I joined the halves. At that point they just confirmed that I didn't have it 180 degrees wrong. In my case a some previous hack had joined the driveshaft about 60 degrees out-of-line, mating to an extraneous mark on the driveshaft, not the white dot.

  4. #4
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    Do the two halves just have to be aligned, or are there also supposed to be markings on the place where they attach to the diff and transmission? What about, for example, my iX, where the driveshaft is only one piece. Do I have to make sure it is aligned properly with the t-case and the diff?

  5. #5
    Join Date
    May 2007
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    87 325e e30
    make your own thread Aaronhoy. There is no need for markings where they attach to diff/tranny. End thread jack.

    DJB2,
    When I had the rear half of the shaft off (not purposfully) yesterday night I looked and could not see any white dots.

    Do you know if the dots will always be concurrent with the U-Joints being phased correctly? i.e. the dots will always make the U-joints be "in-phase"? A yes to this question would make it so there are only 2 possibilities for driveshaft alignment, one being the correct one, the other being 180degrees from correct (if you dont go by white dots).

    Gophers FTW

  6. #6
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    86 325es
    don't worry about it, just go in the classifides here, or on E30tech.com and buy a new rear drive shaft section. I've put mine in about 20 times and never payed one cent of attention to alignment, and even mixed front and rear sections and it never made any vibration even trapping 115 in the 1/4.


    86 325es, 2.8L m50, S476sxe, ProEFI 128 ecu, e85, solid rear axle, TH400 trans, 28x10.5w slicks, zip ties, popsicle sticks, tape
    best time 9.06 @ 151.8 mph, best 60 foot 1.30

  7. #7
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    e36 i e30 ix e46 xit
    Those rear bolts are just knurled and can be knocked out with a hammer and a vise or something like that. Just like a wheel stud in the axel of an old chevy.

  8. #8
    Join Date
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    Joliet,IL
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    87 325is 96 GMC Suburban
    Here is a thought... IF the rear half of the drive shaft is balanced, and IF the front half is balanced, how could it matter how they are put together? Surely the engineers at BMW would not put two peices of shit together then balance it as a unit? That sounds like something Chrysler would do. As usual I am prolly missing something so engineers please chime in.

  9. #9
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    Quote Originally Posted by aaronhoy View Post
    Do the two halves just have to be aligned, or are there also supposed to be markings on the place where they attach to the diff and transmission? What about, for example, my iX, where the driveshaft is only one piece. Do I have to make sure it is aligned properly with the t-case and the diff?
    Only the two halves need to be aligned. There is no special alignment needed to the transmission or differential.

    Even if the two halves end up 180 degrees out, that's better than misaligned joints. U-joints are not constant velocity -- at non-zero angles, the output shaft will change speed when driven by a constant sped input. So they are paired so that the intermediate shaft speeds and slows during the rotation, but the output speed of a parallel output shaft remains at a constant speed.

    Before you install the driveshaft check the centering bushing pressed into the transmission end. This bushing goes around transmission output shaft to keep the flex disk from carrying any off-center loads, which could be misinterpreted as an out-of-balance driveshaft. The rear end of the driveshaft is rigidly bolted to the diff, so no bushing is needed there.

  10. #10
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    Quote Originally Posted by MechE30 View Post
    Also, would I be able to just align the driveshaft in it's correct "phase" (only 2 spline alignment possibilities for this phase) and everything would be good? Do driveshafts always get balanced in phase (as in come from a manufacturer in phase)?

    I've definitely researched, but need some more help. Thanks!
    I'd have the whole thing balanced by a competent specialty shop, when you get it back it will be together, with new u-joints, center bearing, ready to install.

    When I put the 5-speed in my CS coupe, I had to have the drive shaft shortened, so I went ahead and had it rebuilt and balanced. Very smooth now.
    Pat
    ____
    '98 Z3 1.9L + '90 325iCab, '87 535iS_____________
    Quis custodiet ipsos custodes? Hostilis Civitas!

  11. #11
    Join Date
    Feb 2006
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    Grand Forks, ND
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    89 325i S52, 06 Z4MC
    ah, so much wrong info here!

    the balance-

    the 2 drive shaft peices are balanced together. they must be in the same exact location or it will likely vibrate. the simplest thing, as stated was find the white dots. you may have to clean the drive shaft a little to find these, but they should be there. they should be right where it couples together. one right behind the splines, one right behind the CSB. As you stated the Ujoints must be in phase. AKA they must be in the exact same orientation. if your dots are non existent you make have to do this job twice. to teconned and get them perfectly back in phase it to get the front Ujoint perfectly level. like one of the flat sides of the joint, get it exactly level. put the car in gear, this will stop it from rotating out of place. take the rear half and line up the Ujoint in the exact same was as the front one is aligned. now simply take the level and level out the rear joint. slide it back together. the joints are never Perfectly in phase, but just like a degree off.

    this can also be done outside the car if you dont have a small enough level to fit into the trans tunnel.


    the studs-

    go the the junk yard, and find a bad DS. screw nut over the first 4 or 5 threads (not so far on that the threads of the stud go past the face of the nut. what your doing is protecting the threads with this.) of the stud that you need to break free. take a mini sledge. give it a good solid hit. it should be unpressed from the drive shaft now. simply take the nut you put on off and it should be good to go.

    putting them back in.
    knock your other stripped studs out.
    put the new one in as much as possible and A. hit it back in with a hammer, (sometimes difficult to keep the DS from moving around with the hit)
    or B. put a washer or two on the nut and then thread a nut on to it. what your doing is using the nut to pull the stud back into it. slight chance of stripping the stud though.

  12. #12
    Join Date
    Dec 2016
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    marshfield, ma
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    2004 bmw x3

    Rebalancing method

    This message is in response to those of use that have for one reason or another our rear drive shaft has separate and have not marked the two ends before separation and have no marks on the drive shaft placed by the manufacturer as i had. If your rear drive shaft came apart and you put it back together and now notice a vibration starting around 45-55 mph it likely needs to be rebalanced and if you have been hard pressed to find a driveshaft specialist that has attachments to mount your bmw drive shaft to rebalance it for you and you don't want to spend hundreds when yours is perfectly fine if its sleeved back together right then here is a methodology I used to rebalance my drive shaft.

    First jack up the car so all tires are off the ground. Remove exhaust (my tip here is to leave the muffler at the rear of the car bolted on and just slide it out of the way, its much easier to reinstall later). Remove heat shield. Now grab masking tape and wrap around the two halves of the drive shaft on either side of the center support. On the rear half make a reference line, then on the front half mark a zero in line with this mark. Then on the opposite side of the zero mark a 180 (indicating 180 degrees) continue this process around the drive shaft making marks at 0, 22.5, 45, 67.5, 90, and so on until you make it back to 0.

    Now your ready to remove the front half the drive shaft from the flex joint to the center support. Place the reference line at 180 degrees. Tighten the drive shaft back up and the center support. Make sure everything is free from the wheels (including the exhaust if its still hanging). Get in the car, turn it on, turn OFF the DSC and shift through the gears and when you approach 65 hold it there and make note of the vibrations (I used a note pad and the original vibrations I noted as a 5 on a scale of 1-10) now compare the vibrations and grade it. Afterwards do not brake there is no need and your ABS will turn on. Just let the wheels come to a rest and turn off the car. Now get back under the car and remove the drive shaft and rotate to either the 90 or 270 mark and repeat. Grade the vibrations and continue.

    Here's how my grading and process went. 0=5, 180=3, 270 =3, 90=5, (since 180 and 270 where about the same I used that to narrow down where that sweet spot is and went between), 225=1, 247.5=2.5, 202.5=1 (again I am able to narrow down), 213.75=0. Once I reached this point I accelerated the car to 80 mph and felt no vibrations and concluded this must be the sweet spot where my drive shaft is balanced. I replaced all three bolts with new ones since they are one time use bolts. Torque everything back up. Replace heat shield, Replace exhaust. Lower car and take it for a spin!!! Hope others find this useful.

  13. #13
    Join Date
    Dec 2005
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    No e30s, again :(
    that is the way to do it if you don't have alignment marks and no place can balance for you. it sucks and takes some time but you gotta do what you gotta do.
    No e30s again.

  14. #14
    Join Date
    May 2017
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    Bronx
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    E46 Sedan

    Umm I’m getting ready to buy a separated 5 SPEED driveshaft

    [QUOTE=someguy2800;17543845]

    Umm I’m getting ready to buy a separated driveshaft I have a brand center support bearing to put on it and all would it be a problem when trying to use since it’s separated or is it a good to go and just get it balanced ?
    Last edited by Eddie95; 02-18-2018 at 01:23 PM.

  15. #15
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    No e30s, again :(
    Get it balanced if you csn find no marks to align it the way it was before.

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