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BMW 3-Series (E90 E92) Forum
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Wavetrac Installed (6MT) - thud/thump noise when upshift gears
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03-28-2015, 01:47 AM | #155 |
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Yes, you are correct, and will depend on the condition of the axle stubs.
Most quality LSD's will be machined precisely to specification, based on a new set of "unworn" axle stubs i.e if new axle stubs are used, there should be very limited play between the meshing of the splines (there will be a little due to the fact that they are not press fit and just freely slide in and out). If old axle stubs are used, then there will be slightly more play due to wear/compression, and this will contribute to the overall backlash, thus the "thump". Thank you for mentioning this, and I will make sure to include this in the Differential FAQ that I am putting together for the forum |
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03-28-2015, 04:54 AM | #156 |
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From what I've gathered from reading this thread if you only get it putting it into gear from a stop its normal. Wavetrac, quaife and mfactory guys are all getting it. ...if however is happening all the time between gears, not so good.
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03-28-2015, 05:20 AM | #157 |
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When moving, the gears in the LSD and Ring & Pinion are in a constant state of mesh, turning all the time regardless of whether the clutch is engaged or not, so there will always be this free play when changing gear.
The only time that they are not turning is when the car is stationary. However, when stationary and in neutral, your transmission gears are still turning, so when you put it into gear, this locks the gears together causing the propshaft to turn very slightly which causes the "thump" due to the free play between the propshaft turning and the axles turning. As the axles are basically locked into position and can't move due to not enough power being applied (i.e clutch is still disengaged), this is why the thump (i.e vibration) is more noticeable when putting it into gear from stationary, compared to changing gear when moving. Remember, the thump is not "noise" per se, it is vibration through the chassis. |
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03-28-2015, 03:28 PM | #158 | |
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So you are saying that this thump is fixable? Or at least making it less obvious? Do you mind making a list of stuffs that the owner of "thumpy diff" wants to check for? I bought my unit through DiffsOnline, and take it to 3D Autowork (a BMW race car shop..) and wasted another $700 for them to check for the thump and reinstalling and sxxt. At the end they tell me it's from INSIDE the unit, nothing they can do but tell me to contact Wavetrac. When I had it on my car is less than 30,000 miles, few months back. Now I still suffer with this clunky thumping pounding throbbing fxxking diff every morning, really shakes my heart. Already wasted too much money on it... sigh btw, does it happen on a clutch type too? |
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03-28-2015, 03:36 PM | #160 | |
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03-28-2015, 03:38 PM | #161 | |
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03-29-2015, 10:57 PM | #162 |
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It's not the shaft, but the centre bearing on the shaft that is the issue. It's a little bit finicky when bolting back up to the diff, so can be misaligned. Or it could simply be worn.
I will be adding some suggestions to help fix/limit the thump in my Differential FAQ, yes, but in the meantime, the first area to check is the propshaft centre bearing. If all is ok there, check your axle stubs for excess free play (although most that we've seen are within acceptable limits. This is because all the cores we get in are low mileage). once these two are ruled out, only then should you be thinking about looking inside the pumpkin and checking to see if the preload and backlash is within tolerances. also, you need to remember, as with "gear clatter" when installing a new Flywheel, this "thump" is always going to be there, even on a brand new oem pumpkin. How much though (and whether you will hear/feel it or not) will depend on what other modifications have been done. A new clutch will bite harder than a used clutch, so this will contribute to the "thump", even more so with an uprated clutch. Similarly, upgrading to stiffer bushings, stiffer suspension, swaybars, braces etc etc will affect how much "thump" there is. |
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03-30-2015, 12:38 PM | #163 | |
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But it the stub is bad, you need a new half shaft right? |
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03-30-2015, 12:59 PM | #164 |
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1st thing is to check your propshaft centre bearing, and replace if worn
2nd is to check your axle stubs. If these are worn, they will need to be replaced. Your axles can be re-used |
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