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      10-19-2014, 08:51 PM   #1
Joey911
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THUMP from rear end. Just had Wavetrac on

Hi guys,

I have a 2011 BMW 335i M Sport 6MT. I got the whole wavetrac pumpkin from Diffsonline and installed on to my car following Bentley Manual and Torque precisely.

Timeline:
1. Got the the LSD pumpkin and installed the same day, THUMP is loud, thought it's what LSD does normally.

2. The THUMPs was way too annoying, and I could actually feel a delay between my foot and tires (power won't go to the ground until the THUMP occurs, gap in drivetrain??)

3. Took the whole pumpkin off the car (since I haven't return the core yet), and brought it too Diffsonline and have him inspect it, no problem, so he tighten the already perfect backlash to a even tighter spec because I requested it.

4. Put it back on the car, THUMP the same, didn't become softer, so probably not from the ring gear.

We discussed and I researched. dzenno from this forum had a big thread about it and said the thump goes away once he put in a new half shaft (cause the old one cracked)

I assumed the pumpkin has NO PROBLEM at all, what could be the problem? Half shaft? drive shaft? how do I inspect them?

**THUMP when pushing in gear**
I have my car lifted in the shop, clutch in and hold, push in first gear. There's a THUMP from the rear right at the 'push in' moment and the tires will actually rotate maybe 10 cm and stop.

Is it normal that power through driveshaft BEFORE clutch out? It's like the system want to load the gaps or something.

Tests:

I test it when the car was off the ground and have some one look at it under the car. My right foot hold the brake tightly, left foot play with the clutch. 1st, release clutch half way just to engage and make that THUMP, reverse, and release half again and THUMP. *Notice* tires weren't moving.

He said the pumpkin goes up and down around 6mm from top to bottom. Is it a normal range?


My car is getting destroyed by this violent THUMP slowly... I can feel something get loose whenever the THUMP happens.....

Thoughts?


UPDATE 1 (Feb 9, 2016):
Hello guys, sorry that I never posted an update. I will make it short. Basically, I complained about it to Wavetrac right after I had it installed. After a long time, they sent me the REVISED version of the same unit. They claimed they used different gearing, to reduce the backlash.

I was satisfied with the test-drive after the installation, the "gap (backlash, noticeable backlash by driver..)" wasn't a "gap" anymore, I would just called it a.. well still a thump but not entirely super annoying anymore.

skip to the day I changed my front control arms to M3 spec:
(my control arms were worn as f, when i brake, steering wheel would shake left and right, cause the toe angle changes)

The first thing I noticed when I started moving my car was not how much tighter the steering became, it was the weaken "thump"!!

So I concluded to myself, that any weak or worn rubber part on the car (from driveshaft guibo, to diff mount subframe mount, to engine mount, control arms, all kind of rubbers) will amplify the thump, since it allows the shock to keep moving around the car.

And recently, I did the first oil change after a long time, I put in Motul Gear FF Competition 75W140, overload it a little by tilting the car forward, just a little.. it came out good, thump was somewhat weaken again.

Now I am at the point that if no one points out the thump, or unless it's too cold that the thump is amplified, I don't notice it anymore. Maybe I get used to it or upshift and downshift smoother to avoid the thump, but it does not annoy me anymore

Will report after upgrading other rubber parts.

Last edited by Joey911; 02-09-2016 at 09:17 PM..
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      10-20-2014, 04:10 AM   #2
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I can't offer any solutions but I'm very interested to hear what you find. I also have a Wavetrac and "the thump". I'm not entirely sure it is the Wavetrac but I have my suspicions.
If you can afford the time, you could put the old diff back in and see if the clunk disappears - that would definitely indicate that the issue is inside the diff not outside (driveshafts or bushes etc.)
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      10-20-2014, 08:23 AM   #3
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Quote:
Originally Posted by CrustyNoodle View Post
I can't offer any solutions but I'm very interested to hear what you find. I also have a Wavetrac and "the thump". I'm not entirely sure it is the Wavetrac but I have my suspicions.
If you can afford the time, you could put the old diff back in and see if the clunk disappears - that would definitely indicate that the issue is inside the diff not outside (driveshafts or bushes etc.)
I actually did put in the old diff twice. I wasn't aware if the THUMP was there from the beginning probably because it was very soft.

Both the first and second time when I put the Original Diff back on, the can notice a THUMP but very soft (you become sensitive for that THUMP after a loud one)

It has to be somewhere on the rear drivetrain section, but present less with open diff... less stress?
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      10-20-2014, 08:43 AM   #4
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Have either of you though of getting the diff brace that is over on N54tech forums? People are raving about it and it sounds like it may help you guys out. This sounds like drivetrain movement.
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      10-20-2014, 09:40 AM   #5
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Quote:
Originally Posted by JETmn View Post
Have either of you though of getting the diff brace that is over on N54tech forums? People are raving about it and it sounds like it may help you guys out. This sounds like drivetrain movement.
I've seen thread about spending tons of money but still can't get the THUMPing fixed.. I am more interested in pinpointing the exact problem and replace the parts, and the money for JB4 lol

BTW, when I am doing 40 MPH+ slight right, my left side wheels will hum, it's getting louder lately, starting to sound like grinding, does this wheel bearing problem indicate anything?
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      10-20-2014, 10:59 AM   #6
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Quote:
Originally Posted by JoeyWong911 View Post
I've seen thread about spending tons of money but still can't get the THUMPing fixed.. I am more interested in pinpointing the exact problem and replace the parts, and the money for JB4 lol

BTW, when I am doing 40 MPH+ slight right, my left side wheels will hum, it's getting louder lately, starting to sound like grinding, does this wheel bearing problem indicate anything?
The brace is $200 and would really help narrow down the problem. Lots of guys saying they are getting much better traction and less wheel hop also.
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      10-20-2014, 05:23 PM   #7
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Quote:
Originally Posted by JETmn View Post
The brace is $200 and would really help narrow down the problem. Lots of guys saying they are getting much better traction and less wheel hop also.
I emailed Wavetrac tech and they said it could be the "preload of the driveshaft", he said if the driveshaft center bearing is not correctly loaded (I'm still not quite sure) it will have the symptoms even you put the original diff back, now I remember my car was perfect before the first pumpkin swap.

NOISE:
I notice a new noise on my 335i, same noise my old E46 made after the Diff installed. It's like, on flat ground, no ebrake, put in first gear, and let go half of the clutch till in JUST engage, something goes make a loose sound. Push in the clutch, sound is gone, let go half way again, li li li li li noise (don't know how to describe lol)

I will have a video of the noise up soon! I suspect it's what Wavetrac told me, the driveshaft!
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      10-21-2014, 07:06 AM   #8
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Man what a nightmare. I can imagine the thrill of getting this after shelling out probably close to $3k then you install it and no go. Talk about a PITA. You will get it sorted out but I feel for you. I know that when you encounter stuff like this it feels like it is ruining your life until it is resolved.

I am seriously having second thoughts about ordering an LSD and doing the install myself. I previously had thought it would be an easy install and the crux of the event would be figuring out how to ship back the old pumpkin. Perhaps not...
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      10-21-2014, 07:57 AM   #9
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Quote:
Originally Posted by JETmn View Post
The brace is $200 and would really help narrow down the problem. Lots of guys saying they are getting much better traction and less wheel hop also.
I believe his car has the small diff, which the brace doesn't work on.

If you have a GoPro camera, stick it under the car pointing at the pinion where the driveshaft meets the diff. If you see excessive rotation of the diff when it makes that clunk, then a brace would definitely help - if you can find one that fits.
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      10-21-2014, 08:12 AM   #10
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Quote:
Originally Posted by MadToy View Post
I believe his car has the small diff, which the brace doesn't work on.

If you have a GoPro camera, stick it under the car pointing at the pinion where the driveshaft meets the diff. If you see excessive rotation of the diff when it makes that clunk, then a brace would definitely help - if you can find one that fits.
Joey is 6MT, so it should be the large diff. I think only the AT's have the small diff.
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      10-21-2014, 08:29 AM   #11
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Quote:
Originally Posted by JETmn View Post
Joey is 6MT, so it should be the large diff. I think only the AT's have the small diff.
Ah - Then I would definitely start with the brace.
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      10-21-2014, 10:18 AM   #12
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Quote:
Originally Posted by Dan_Q View Post
Man what a nightmare. I can imagine the thrill of getting this after shelling out probably close to $3k then you install it and no go. Talk about a PITA. You will get it sorted out but I feel for you. I know that when you encounter stuff like this it feels like it is ruining your life until it is resolved.

I am seriously having second thoughts about ordering an LSD and doing the install myself. I previously had thought it would be an easy install and the crux of the event would be figuring out how to ship back the old pumpkin. Perhaps not...
Supposed to be very happy like my old E46

There's no official post of people who got it all sort out.. I don't know..
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      10-21-2014, 10:21 AM   #13
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Quote:
Originally Posted by MadToy View Post
Ah - Then I would definitely start with the brace.
Well the diff go top to bottom around 6mm, would that be the thump? and btw my car has 27,000 miles on it.

I will upload a video of that lik lik lik lik noise when half clutch and the car tires to move.

How about PRELOADING the center bearing of the shaft? or alignment of rear shaft into diff?
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      10-21-2014, 10:56 AM   #14
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http://www.e46fanatics.com/forum/sho...d.php?t=855233

useful thread, same thump as me
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      11-05-2014, 11:23 AM   #15
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UPDATE:

So I bring my car in to a shop, wasted 800 dollars, cars still drive weird feels weird comparing to when the first time I get the car.

They said Diffsonline even swap the new Wavetrac unit, but I thump the same.

Emailed Wavetrac, they say it has to be something else wrong cause the unit won't do this noise? But the BMW specialist shop I went to can't find anything else is wrong? Wtf?

This sucks really bad
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      11-05-2014, 03:51 PM   #16
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Damn dude that is a nightmare! I hope someone can help you get this resolved!
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      11-05-2014, 11:07 PM   #17
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Quote:
Originally Posted by Subaru335i
Damn dude that is a nightmare! I hope someone can help you get this resolved!
The more I drive it the more I think something is so wrong.... It jerk so badly when engaging the clutch that I can't drive smooth anymore even if I try so hard
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      11-18-2014, 05:14 PM   #18
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If the bearing pre-loads are not tight enough (pinion bearings and diff bearings), the backlash will increase when the diff is under load, but will measure up in tolerance when measured static with the diff on the bench, unless a lot of torque is applied to the crownwheel (with the pinion held tight to stop it rotating) when checking the backlash.
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      11-19-2014, 02:18 PM   #19
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^ That makes sense. It does sound like something is wrong with the diff.
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      11-28-2014, 09:52 PM   #20
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Quote:
Originally Posted by JoeyWong911 View Post
The more I drive it the more I think something is so wrong.... It jerk so badly when engaging the clutch that I can't drive smooth anymore even if I try so hard
What was the backlash measurement?

If it's thumping and jerking I bet it's way too big and out of limits.
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      01-02-2015, 09:17 PM   #21
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any updates? by any chance you found the fix?

I just installed MFactory diff and have the same issue as you describe.. So far only 200 miles, but I doubt it will go away
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      01-12-2015, 11:37 AM   #22
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Quote:
Originally Posted by danas
any updates? by any chance you found the fix?

I just installed MFactory diff and have the same issue as you describe.. So far only 200 miles, but I doubt it will go away
Wavetrac told me they found nothing wrong in the diff, and will do further more test... And hasn't reply me since then, I'm still trying to email Dana, but no reply

I'm here in New England, I notice the thump will be super soft when it's so cold etc under 32F, or after I drift on dry road for like 10 minutes (things heat up)...
then the thump is basically gone, not annoying or noticeable for a while

But once starting driving for a while (in cold, things warm up), or drive normal for a while after drifting (things cool down), thump will come back again!!!!!! So annoying

So I'm thinking could the viscosity of the diff fluid soften the problem a little..?
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