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07-26-2018, 07:56 AM | #1 |
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New sound...trying to figure it out -not the CSB...brakes!
UPDATE: Replaced the CSB...no effect. Finally popped off the front calipers (which I should have done FIRST...stupid me)...and I am pretty sure it is the brakes - https://www.1addicts.com/forums/show....php?t=1533946
This is a video of my last track day. I am trying to figure out what the "stuttering" sound you hear on all the hard braking sections. Pretty sure it is wheel/tire related as it sounds like it tracks to speed, not RPM. The mic is right near the muffler but you can feel/hear the stuttering in the seat. Pretty sure it's not ABS as you don't feel it in the pedal(and I wasn't braking that hard to trigger ABS). Any thoughts would be appreciated. Tires are RE-71s with 6 track days on them. Temps were hot (90F). I am also starting to experience some rubber scrubbing in the front in the hard turns as the outside edge of the fronts are getting worn (will be swapping tires this week to put the better side to the outside to even wear) but this is different. My biggest concern is that it might be a brake issue but the brakes felt fine the whole time.
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07-26-2018, 07:19 PM | #2 |
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So, it's not track wheels/tires. With the stock wheels/tires I can hear it...maybe a warped rotor? Guibo? Dunno. Need to get under the car this weekend and inspect some stuff.
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08-18-2018, 11:01 AM | #3 |
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Finally got under the car...after a lot of listening and research I think it is the Center Support Bearing. The Guibo got replaced for a recall less than 12 months ago by BMW so I figured that either BMW screwed up installing it, or it couldn't be the issue. The first bit of Bad news...first time I've gotten under the car to see the driveshaft and...of course you can't because the exhaust and heat shield is in the way (I know...I'm a n00b). Second bit of bad news...What I could inspect on the GUibo looked brand new so I don't think that I can blame BMW for this. I inspected the driveshaft connection to the diff and, of course, it's the single large nut design not the 4 bolt design so...ug (I have read i need a special tool).
So, would appreciate any advice...planning this job for labor day weekend when I have several days to deal with it as I am a "in the garage with jackstands" mechanic. What i have learned from the interwebs: 1. Disconnecting the exhaust is straightforward, but be sure to replace all the gaskets (maybe this is the time to upgrade to a Berk Race!!) - so I need to order those. 2. Car has 90K and replacing the CSB requires a bearing puller/pusher (which I don't yet own), however, I can get a complete replacement driveshaft with CSB installed from places like www.driveshaftspecialists.com for less than $500 and refresh the whole thing while I am under there(problem could be a U-joint on the driveshaft as well so this would fix that). 3. My driveshaft rear locknut requires some kind of expensive special tool to get it off. I did see that there are several aftermarket tools (ECS has one, I believe) but am not sure how good any of those are. Should I just buy the BMW tool and be done with it? So the decision is really between not ordering parts and just doing discovery labor day weekend and the car being out of commission until I get the specific parts I think are bad, or just planning to replace the entire driveshaft and do that on the same weekend(at the risk of "wasting" $500). Help from anyone who has already been down this road would be much appreciated!
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08-18-2018, 11:46 AM | #4 |
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OK...figure since I am getting under there I will do transmission mounts...are the mounts the same for manual/auto/DCT? I don't see any differentiation at ECS...
Any recommendations? Thx!
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08-18-2018, 11:57 AM | #5 |
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LSD?
I need to find some headphones and listen again. All I am hearing through computer speakers is exhaust burble, sometimes caused by a leak, or exacerbated by. My MFactory unit was making strange sounds until I found a fluid it liked. Tried Red Line Lightweight shockproof, didn't want to lock/unlock as well as I thought it should. factory BMW non-LSD fluid, better reaction but still felt sluggish. Redline super light weight shockproof, perfect. |
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08-18-2018, 12:07 PM | #6 | |
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Really prevalent at 0:48-53 at 1:20-1:22 I am on maintenance throttle and you can hear it also.
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Andy '12 E82-PS2,Stoptechs,Clubsports+M3 bits,Accusump,Wagner DP+EVO III FMIC,ERCP,BMS Intake,Mason Strut Bar,Wedge Tune Last edited by AndyW; 08-20-2018 at 11:37 PM.. |
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08-19-2018, 03:07 AM | #7 |
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See any odd ware on the rotors? Ive seen defective pads make the same exact noise. Something to do with improper mix of the compounds will cause excessive build up of metal in parts of the pad and chatter. Could also be warped rotors, id check them with a dial gauge if possible
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08-20-2018, 11:36 PM | #8 | |
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08-23-2018, 08:24 PM | #9 |
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Well, it's not warped rotors. Sigh. Was kinda hoping.
Checked two races of data points (one toward the center, one toward the outside) on each rotor with a dial micrometer...no more than 0.0002" deflection on any of them. Close to needing new pads tho...so there is that...lol. Next I drop the exhaust and heat shield to inspect the driveshaft CV's, guibo, and CSB. |
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08-24-2018, 09:20 PM | #10 |
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So, it looks like the guibo and universal joint are OK. Didn't remove from the car but took some pics and video of the CSB movement. Really just need a practiced eye to tell me if the CSB has too much movement or not. I also noticed the "grease dirt" line around the universal joint, but the joint itself did not look dry.
On a related note...if I want to remove the Guibo, do you put the car in neutral to rotate the driveshaft to get to the upper Guibo nuts or just an angled wrench? Bentley Manual isn't specific as to the method, just that you undo the nuts on the transmission side...which are of course, hard to get to... Center Support Bearing. Videos of movement: Guibo. Universal Joint.
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08-26-2018, 05:00 PM | #11 |
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The guibo and the u-joint look perfectly fine, so I think you're on the right track looking into the center support bearing. Personally, mine was ruined because after uninstalling the driveshaft to install a new clutch, I bolted up my CSB upside down. The rubber portion of mine was ripped all the way through, where yours seems to be intact.
Yours is oriented correctly, but I'd still be uncomfortable with that much play in the center support bearing. Ideally, that should not have any play. And would make sense considering the sound on hard braking if the torn rubber is allowing the driveshaft to shift forward. The only part that doesn't make sense to me is that you're getting no vibrations under heavy acceleration. From all my research, that should be happening if your CSB is shot or nearing the end of its useful life. Regardless, I'd probably just order a new OEM BMW CSB, throw it on there, consider it maintenance, and see if that fixes things. It certainly wouldn't hurt. Put the car in neutral to rotate the driveshaft. Also, I wasn't aware of any driveshaft recalls. Why exactly was the guibo originally replaced? Was it an aluminum version? |
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08-26-2018, 06:17 PM | #12 | |
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The problem on all this will be if the sound remains AFTER I replace the CSB (where to go next?). Neutral is a bit more a pain with DCT...but I know how... It was a guibo recall...I honestly don't know what the original one was. They just told me it was needed when I had it in for other service (airbag recall). Car has a 4/11 build date. The transmission mounts look pretty good...I think I will forgo the mounts upgrade at this time (although the Turner engine mounts looked pretty cool!). Planning on LSD this winter so that will be a good time to go poly everything to match my RSFB's! The Bentley manual says to replace the bolts when you replace the guibo, but since I am just uninstalling and reinstalling to facilitate replacing the CSB, should i do that? The torque is only 55N-m on those.
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08-26-2018, 07:25 PM | #13 | |
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I've installed/removed the guibo 3 times now, and am still using the original bolts and nuts. No issues that I've noted with reusing, but yes, technically they should be replaced. |
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08-28-2018, 10:16 PM | #14 |
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Decided to replace the rear diff fluid while I wait for the new CSB to arrive...man that stuff was dirty!
I also started the car and rolled the driveshaft up to 20mph... everything looks fine. Car is LOUD without any pipes...lol. |
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08-29-2018, 11:08 PM | #15 |
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Need to remove the transmission mount assembly to properly get to the guibo nuts on a 135. Sigh...always harder than you think..
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09-03-2018, 08:19 PM | #16 |
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If you have a DCT, this is harder. Have to remove the entire transmission mount assembly to get to the guibo nuts. Also...a three arm puller didn't work...not enough space between the bearing and the u-joint for the puller fingers to fit. Sigh. So I am ordering these.
OTC 4518 Stinger 5-ton Bar-Type Puller/Bearing Separator Set https://www.amazon.com/dp/B0002SR47M..._o2DJBb7DT7VQ0 |
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09-08-2018, 01:01 PM | #17 |
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With the correct tool it came out fine. Put the new one in and everything buttoned up...man, what a pain to get to this thing! First drive it seems OK. Not sure if sound is gone. Need to get on the highway. Crossing fingers!
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