Rumble and vibration after Wavetrac install

[Rbohn1]

Hey everyone,

New member here but long time lurker. I will properly introduce myself and my car in a separate thread soon if anyone wants to know more about it. I hope I'm posting this in the right section, but anyways onto the issue at hand.

I recently installed a new Wavetrac differential with the 3.46 ring and pinion in my 2012 135i 6mt, and from the very first drive after the install there has been a deep rumble/chattering noise coming from the rear of the car. The strange thing is that the noise is only present while cruising or coasting in 5th gear between 2000-2500rpm. When I'm cruising in 5th between that rpm range and am just maintaining does with the throttle, the noise is somewhat hard to hear. However If I'm coasting in 5th (off throttle with car in gear) within the same rpm range, the noise becomes significantly louder and deeper pitched. When I completely let off the gas while coasting, as the car slows down and tach drops closer to 2000rpm the noise will begin to oscillate or chatter similar to the way a straight cut gearbox sounds when you lift off the throttle, and the pace at which it oscillates or chatters slows down as the rpm drops further. Once the tach drops below 2000rpm the noise vanishes, and same goes for when I throw it in neutral or push in the clutch. I can also feel a slight vibration throughout the car whenever the noise is present, but it's very minor and hasn't seemed to get any worse over time

Now I should probably mention that I also installed Condor Speed Shop UHMW subframe and differential bushings at the same time as the new diff, but considering this issue is limited to just 5th gear I don't see how these could be the culprit. In fact, despite the subframe/diff bushings essentially being solid the only increase in NVH I've experienced in any driving scenario other than what was mentioned above is a very slight diff whine. If the rumbling noise was coming from the diff I would think it would be present regardless of what gear I'm in, but perhaps the backlash wasn't set tight enough when the diff was built? I've tried contacting Wavetrac to find out what they set the backlash to, but have yet to hear back.

I'm hoping someone in here has experience with a similar issue and would be willing to share what the problem or fix ended up being. My best guess is that I accidentally damaged the driveshaft center support bearing during the install, causing the driveshaft to bounce around. The only thing I can think of as to why I only notice it in 5th gear is that maybe that specific gear ratio is generating a certain load or resonance in that rpm range, causing the driveshaft to vibrate or bounce around thus producing the rumbling noise. I haven't had a chance to get under my car to confirm anything yet, so these are just theories for now. It could also be my 5th gear synchro going out, but that wouldn't explain why the noise is coming from the back of the car.

So I'd really like to get your guy's opinions on what the issue could be, should my guesses be incorrect. Based on my description, do you think there's anything I can officially rule out anything as a potential culprit? Anything else I should look for when I am able to get back under my car? I would greatly appreciate any help or advice you guys can offer!

[iminhell1]

Did you do a complete assembly or did you just buy the carrier and do a self install?


Sounds like it could be a backlash issue.

[jwolf]

Was the flex disc maybe damaged when the shaft was dropped. It may have been fine until stressed during the process.

[Rbohn1]

Originally Posted by iminhell1

Did you do a complete assembly or did you just buy the carrier and do a self install?


Sounds like it could be a backlash issue.

I bought a complete carrier that was built by Wavetrac, at least according to Evolution Racewerks. I did install it myself but I took it slow and was pretty meticulous about it. I was thinking backlash at first too, but I wouldn't the noise/vibration be present in other gears besides just 5th? 1st-4th gear feel totally normal apart from a slight diff whine. But keep in mind the diff/subframe bushings I installed at the same time as the new diff are basically solid, so a bit of diff whine is normal. The noise I'm talking about is something else though.

[Rbohn1]

Originally Posted by jwolf

Was the flex disc maybe damaged when the shaft was dropped. It may have been fine until stressed during the process.

I'm not sure, I didn't completely pull the heat shielding during the install so I never got a look at the guibo or even touched the front half of the driveshaft. I didn't even think to inspect it because I never had any issues with it prior to all this. My car does have just over 130k miles though so I'm sure the guibo was probably almost due for replacement anyways, and I wouldn't be surprised if wrenching on the giant nut where the driveshaft connects to the diff could have accelerated the issue.

I didn't actually remove the driveshaft or drop it on the ground at any point though. I just tied the end of driveshaft up while I had the diff/subframe out. But I had to cut the driveshaft down and slip the end of it onto the connection to the diff in order to get it properly positioned and bolt it in, and I accidently pulled the diff a bit too far back causing the end of the driveshaft to slip off and hang freely. I immediately grabbed it and tied it back up, but the center support bearing took all the weight when it fell which is why I think that could be the issue. Not to mention the driveshaft hung at like a 90 degree angle when it slipped off, and I don't think that joint is designed to flex that much..

I decided to just order a new center support bearing and guibo anyways since they're likely overdue. Looks like everything will be here in Friday so hopefully I'll get a chance to install them over the weekend and report back.

[iminhell1]

Originally Posted by Rbohn1

I bought a complete carrier that was built by Wavetrac, at least according to Evolution Racewerks. I did install it myself but I took it slow and was pretty meticulous about it. I was thinking backlash at first too, but I wouldn't the noise/vibration be present in other gears besides just 5th? 1st-4th gear feel totally normal apart from a slight diff whine. But keep in mind the diff/subframe bushings I installed at the same time as the new diff are basically solid, so a bit of diff whine is normal. The noise I'm talking about is something else though.

Yes and no.
When you're engine braking in 1-4 it could be there's enough of a load on the diff that it's keeping a the gears tight; if it's a 1.5/2 way the clutches stay locked. That would mean 5/6 just don't have enough load the keep the clutches loaded, they unlock and you hear the out of spec backlash.
Just speculation though. And most just get the standard 1 way diff.

If you have a potentially sacrificial gopro, strap it under the back and see if you can video something moving or deflecting.



*edit*
Just looked at ER's site. They make no indication if the diff they sell is clutch or gear, but by price I can say it's gear. That also means it's a 1 way, so no lock on decel/engine brake (or shouldn't be).

So my theory is a total bust.
Best I can offer now is play with fluids. The diff works on friction/stiction. You can raise or lower the viscosity to change how the diff engages and being we're playing with multiviscosity fluids, temp will play a role also.
I'm on the MFactory 3.46 in my auto. I tried the factory BMW fluid, didn't like it. Too thick and diff was very slow to react on corners.
Redline lightweight Shockproof, far better than the BMW stuff, but still a lazy diff IMO.
Redline super lightweight, just perfect IMO. The diff was seamless. I didn't have that .5 sec delay that I did with everything else. Just felt natural.

You're not going to hurt anything playing with fluids. It's costly yes but you can change how the diff reacts. Might be worth a shot?

[Rbohn1]

Yeah I'm pretty familiar with how all the different types of differentials work and their advantages/disadvantages. I have the Wavetrac differential which is a helical, so there's never actually any locking going on inside the differential aside from the wave feature that supposedly will quickly lock the diff if you lift a wheel mid turn allowing it to transfer torque to the wheel that still has traction, unlike other helicals which will just send all the power to lifted wheel. Now as for how well this feature actually works is anyones guess, I just thought it might be a bit more capable than the other helical options in poor weather conditions seeing as I live in Colorado.

I've tried out all sorts of fluid in my transmission after I got my new clutch/flywheel installed, so I have a good idea of the types of fluid I like. Again, living in Colorado makes it difficult to find a fluid that is suitable and works well for all weather conditions. I've tried everything from redline, royal purple, motul, liqui moly, and factory BMW fluid, and Liquid Moly put everything else to shame honestly. I tried Redline MTL and I really wanted to like it, but that fluid was awful in the cold. It would take like 20 minutes of driving before the gearbox would stop sounding like it was about to grenade and cold shifting would make cringe. I've used Redline MTL in multiple cars in the past and never had any complaints, but this car really didn't like it for some reason. I swapped it for the liqui moly and it made my transmission feel brand new, and I swear significantly reduced the chatter from my single mass flywheel somehow. After that I switched all my fluids to liqui moly (side from brake fluid) and haven't looked back since. I'm currently running their 75w-90 GL5 fluid in my diff, but I finished the break in period not too long ago so I do need to throw some fresh fluid in. My plan is to do that, replace the center support bearing, and replace the guibo this weekend assuming all my parts arrive in time. These are all great inputs though!

[iminhell1]

It's tough to judge how car savvy someone is from a few posts. But sounds like you're like me, play play play. My type of people.
And I totally hear ya on the fluid temp thing. I need something that works from about 100*F to -40*F, LOL.

I'd played with the wheel in the air on mine. I have just enough of a hill in my yard I can do this. Wheel in the air, no traction. The diff needs resistance to transfer power, no resistance no transfer. So tap a brake or drag a brake and it'll transfer.
OR, do the easy and no need to think thing and leave the stock EDiff active. That's what I did and it made me happy. But for some odd reason the coding on mine was screwed up, there was something about clockwise or CCW option and mine was checked wrong. Once fixed worked awesome .... so I was playing with INPA and watching wheel speeds and rotations. Front was correct but rear was switched. Probably something I did by accident or something with an update.

Also, my major track time is from ice racing. So little to no grip and tons of drifting. My experience comes more from to edge or to no grip vs the normal track guy who is looking for grip and rarely on the edge of.
I'm really an oddball, and far as I know the only person who's ice raced a 135i.

[Rbohn1]

Originally Posted by iminhell1

It's tough to judge how car savvy someone is from a few posts. But sounds like you're like me, play play play. My type of people.
And I totally hear ya on the fluid temp thing. I need something that works from about 100*F to -40*F, LOL.

I'd played with the wheel in the air on mine. I have just enough of a hill in my yard I can do this. Wheel in the air, no traction. The diff needs resistance to transfer power, no resistance no transfer. So tap a brake or drag a brake and it'll transfer.
OR, do the easy and no need to think thing and leave the stock EDiff active. That's what I did and it made me happy. But for some odd reason the coding on mine was screwed up, there was something about clockwise or CCW option and mine was checked wrong. Once fixed worked awesome .... so I was playing with INPA and watching wheel speeds and rotations. Front was correct but rear was switched. Probably something I did by accident or something with an update.

Also, my major track time is from ice racing. So little to no grip and tons of drifting. My experience comes more from to edge or to no grip vs the normal track guy who is looking for grip and rarely on the edge of.
I'm really an oddball, and far as I know the only person who's ice raced a 135i.

I've heard about the tapping the brake trick but that seems like something much easier said then done, especially in a racing scenario where you might only lift a wheel for a split second. But I only really care about the no-load feature on the Wavetrac for driving in the snow, and I figured that feature might help the diff distribute power more evenly/predictably in oversteer situations. I'm not necessarily going for all out grip or trying to shave milliseconds off my lap times though, just trying to make this car as fun as possible and feel like a proper sports car, and there was no way that was ever going to happen on the factory open diff.

As for the E-LSD I wanted to eventually try coding mine out. I'm still pretty clueless when it comes to that stuff though and haven't really taken the time to learn about INPA yet. My last car was a Nissan 350z which didn't have anything like that, so I didn't even know INPA was a thing for the longest time until I stumbled across a thread where someone mentioned coding out a bunch of features. So as someone who was mainly used to working on 90's-early 2000's Japanese cars, trying to make sense of this initially and just trying to understand all of the electrical systems of this car in general was like trying to read an alien language that was written in braile haha. Anyways, I'd love to be able to code the E-LSD so that it only turns it off when the DSC is turned completely off, but I don't know if that's even possible. If you happen to know of any good resources for people who are new to coding or INPA please feel free to share.

And that's awesome you take your 135i ice racing, I'm sure that's an absolute blast. I'm guessing you use studded/spiked tires for that? I could see myself getting totally hooked on that if I ever get to try it out. Anytime we get a decent snow here I go out and search for any big empty parking lots or open roads that I can find and just drift around, sometimes for hours at a time. It's totally childish, but I don't think it will ever get old haha.

[iminhell1]

For an easier option Use ProTools. It's a safer option because it will make backup files automatically. Mess up, just revert to stock.
https://www.bimmergeeks.net/protool

Or you could go the Carly route. But TBH, it's getting to be on the expensive side. I got into that one early and it was cheap for me, and I'm grandfathered into a lifetime pro license.
https://www.mycarly.com/brands/bmw/

If you don't have inpa (standard tools), you can also get that from Bimmergeeks.
https://www.bimmergeeks.net/downloads


far as what to code off:
https://www.1addicts.com/forums/show....php?t=1216642

[dtla1]

Originally Posted by iminhell1

Also, my major track time is from ice racing. So little to no grip and tons of drifting. My experience comes more from to edge or to no grip vs the normal track guy who is looking for grip and rarely on the edge of.
I'm really an oddball, and far as I know the only person who's ice raced a 135i.

I'm just here to say we will want to see some videos of your 135i ice racing. That sounds freaking awesome man. I always thought your profile picture was you just messing around in the snow, didn't realize it was actual ice racing!

[Rbohn1]

Originally Posted by iminhell1

For an easier option Use ProTools. It's a safer option because it will make backup files automatically. Mess up, just revert to stock.
https://www.bimmergeeks.net/protool

Or you could go the Carly route. But TBH, it's getting to be on the expensive side. I got into that one early and it was cheap for me, and I'm grandfathered into a lifetime pro license.
https://www.mycarly.com/brands/bmw/

If you don't have inpa (standard tools), you can also get that from Bimmergeeks.
https://www.bimmergeeks.net/downloads


far as what to code off:
https://www.1addicts.com/forums/show....php?t=1216642

Wow I was expecting like a single link, maybe two. This is awesome though thanks for sharing these! Looks like I have homework to do.

Also I agree with dtla1 about wanting to see this ice racing in action. Honestly wouldn't be mad if you thread jacked me with a bunch of ice racing videos haha