[Joey911]

still no answer from Wavetrac... for over a month

[stephenf121]

Hate to revive a dead thread, but was a fix ever found for this? My car is having the exact same symptoms after a wavetrac lsd was installed. After researching every thread ever made on this i still haven't found a solid answer. The only thing that i have seen that fixed it on two peoples car was proper drive shaft installation. They said that if the installer didn't rotate the drive shaft into the original position it came out at, that the thump would occur.

[Joey911]

Originally Posted by stephenf121

Hate to revive a dead thread, but was a fix ever found for this? My car is having the exact same symptoms after a wavetrac lsd was installed. After researching every thread ever made on this i still haven't found a solid answer. The only thing that i have seen that fixed it on two peoples car was proper drive shaft installation. They said that if the installer didn't rotate the drive shaft into the original position it came out at, that the thump would occur.

No, it's the backlash inside.. Although I did something to the other part of the car and reduced the "thump" power.

My 335i front control arms were shot, leaked all the oil, so I upgraded it to M ones. Surprisingly in my case, it reduced the overall thump quite a bit. For real!

So I'm guessing, that the "shock" (from the backlash, and cause a thump) will go through your WHOLE drivetrain, any worn rubber part will help the thump to be more significant (cause even more loose parts)

That's my theory... I'm not sure how an upgraded rubber mount part (more solid mount, engine to tranny to diff...) will impact the thump level.


Im putting on some tranny mount soon, the black one from UUC, I'll post it here if I remembered or anyone asked lol

[stephenf121]

Thanks for quick response man, I will definitely give that a shot! my car has a differential locking brace and polyurethane bushings, the installer of the lsd blamed the thump on those... had another shop look at it and they said the backlash was fine so they didn't know what was causing it. M3 front control arms will be a good mod even if it doesn't help, so I will give that a shot i guess!
Back to the driveshaft installation, one guy said when he rotated the driveshaft back to its original position before installing in, his thump went away. He said according to the manual, the driveshaft should be torqued to the differntial first, then torqued to the back of the transmission. He said many installed reverse this process and don't mark the driveshaft when removing it and that some how causes the clunk... i want to try but am afraid it'll cost a lot and might not work...

[Joey911]

Originally Posted by stephenf121

Thanks for quick response man, I will definitely give that a shot! my car has a differential locking brace and polyurethane bushings, the installer of the lsd blamed the thump on those... had another shop look at it and they said the backlash was fine so they didn't know what was causing it. M3 front control arms will be a good mod even if it doesn't help, so I will give that a shot i guess!
Back to the driveshaft installation, one guy said when he rotated the driveshaft back to its original position before installing in, his thump went away. He said according to the manual, the driveshaft should be torqued to the differntial first, then torqued to the back of the transmission. He said many installed reverse this process and don't mark the driveshaft when removing it and that some how causes the clunk... i want to try but am afraid it'll cost a lot and might not work...

Good point for the original position and the installation order of the driveshaft.

For the original position: since I got the whole pumpkin, there were no original position for the driveshaft to land... So I don't know this one.

The installation order: I do have Bentley menu, let me check it up and edit the post in a minute.


BUT!! I got a video of the clunk when the car is off the ground (actually it can make the same noise when the wheels are on the ground too). IF YOU engage it really hard, you CAN HEAR A METAL TO METAL CLUNK LOUD AND CLEAR from inside of the diff! Whenever I remember this, I don't know what else to blame but the backlash inside....... People say by the design of gear type LSD, there will always be backlash because the steel inside expand when heating up (I'm not confirming it)

Umm what's next?

[SUPAN]

Why dun get Quaife ?hehe

[stephenf121]

good point on the backlash... its just crazy two shops both say my backlash is fine... not sure where to go from here. As my car warms up, i think the thump get louder, i wonder if i a different gear oil would change that? One of my buddies recommended a gear oil additive, i forget which one though, i might look into that as it could be a cheap fix.

[Joey911]

Originally Posted by stephenf121

good point on the backlash... its just crazy two shops both say my backlash is fine... not sure where to go from here. As my car warms up, i think the thump get louder, i wonder if i a different gear oil would change that? One of my buddies recommended a gear oil additive, i forget which one though, i might look into that as it could be a cheap fix.

I looked into the additive thingy a while ago, mostly for clutch type cause it's "friction modifier." Really not sure if it helps gear type, didn't find one single answer.

Wavetrac specifically says don't use the Redline shockproof oil! If you were thinking of a thicker oil way, which I am going to, just use their recommendation, Motul competition, the 140 one.

[Joey911]

Originally Posted by stephenf121

good point on the backlash... its just crazy two shops both say my backlash is fine... not sure where to go from here. As my car warms up, i think the thump get louder, i wonder if i a different gear oil would change that? One of my buddies recommended a gear oil additive, i forget which one though, i might look into that as it could be a cheap fix.

And btw, only owners of manual transmission experiences this. Most of the Auto or DCT guys have no thump at all.

[stephenf121]

ill give that type of gear oil a shot, maybe that'll help a little!

[Ozzie335i]

Originally Posted by stephenf121

ill give that type of gear oil a shot, maybe that'll help a little!

It won't.

[stephenf121]

any ideas then Ozzie? Im willing to try the cheap stuff first, you never know what might help since no one can figure it out...

[trixdout]

Your backlash is not set correctly. Whoever may have installed your pumpkin, may have done it incorrectly. If the pumpkin was all set just need to be bolted in, then the backlash was set bad from the start. Get it checked out.

Incorrect backlash can cause this thumping whenever you apply throttle from a stop. If you try and launch the car really really hard, you can shear the teeth on the ring gear. Be careful.

[stephenf121]

The differential has been inspected by two shops, and both said the backlash was set correctly...

[Ozzie335i]

Hi Stephen. I have the MFACTORY 3.46. I too have gone through this, and like many others, am living with it. Having the Dinan short shifter and some music or right wing hate radio on masks the thump when clicking the shifter into first.

trixdout, this sound occurs when the clutch is engaged and the shifter is first put into first gear.

[Joey911]

Originally Posted by trixdout

Your backlash is not set correctly. Whoever may have installed your pumpkin, may have done it incorrectly. If the pumpkin was all set just need to be bolted in, then the backlash was set bad from the start. Get it checked out.

Incorrect backlash can cause this thumping whenever you apply throttle from a stop. If you try and launch the car really really hard, you can shear the teeth on the ring gear. Be careful.

I went through 3 set of Wavetrac LSD unit, 3 installations, long story begins:

All the work inside of the pumpkin was done by Diffsonline, they are local to me.

First off, I got the whole pumpkin with Wavetrac from Diffsonline the first time, I was there while he was installing it. He checked all the backlash (between ring and pinion gear) to spec. Brought it home, and installed in a shop. First thing I noticed is the terrible thump when reversing the car out... Instantly pulled the car back up on the lift to check if everything was tight.

So I complained about it and remove the pumpkin and bring it to Diffsonline (lucky I still have stock ones). I already researched a lot about thumping noise by that time, so I have him check the backlash, and tighten it, and he also put in a new LSD unit from Wavetrac, and sent the one I have back to them. This time I have him tighten the backlash even more. After installation, the tighter than normal backlash did make a difference... The car got dragged by the diff a lot, very noticeable when I lifted off throttle, the car will decelerate very quickly. Second, it whine from time to time. Lastly, the thump is not improved AT ALL!

Wavetrac took my first LSD unit and do branch test. It took forever, like few months, until they tell me they did find noise in the LSD on branch test, will work on it.

And exactly half a year later, they sent a new unit to Diffsonline, and I brought in the pumpkin again. This time, the thump is significantly reduced due to the revision of the internal gears. Basically, the backlash is INSIDE of the LSD unit, since it's a gear type LSD. But problem is not 100% gone, but a night and day difference. It still thumps, but the slack in drivetrain (slacking back and forth if RPM does not match perfectly when downshifting) is not as much as the first time, and I'm set with it, don't want to do anything more.

Never heard and review about Diffsonline... I assume he knows the diff better than us...?

[Offset Motorwerks]

Ah, the rear end thump. We see it often. I have seen diff bushings/bolts come loose (seems to happen more with poly bushings), rear control arm bolts come loose, Axle CV's worn out, and a defective LSD once. Funny how it all sounds very similar inside the car. Check everything. I highly doubt it's the diff itself.

[Joey911]

Originally Posted by Offset Motorwerks

Ah, the rear end thump. We see it often. I have seen diff bushings/bolts come loose (seems to happen more with poly bushings), rear control arm bolts come loose, Axle CV's worn out, and a defective LSD once. Funny how it all sounds very similar inside the car. Check everything. I highly doubt it's the diff itself.

Agreed! Cause changing my front control arm actually soften the problem

[stephenf121]

I just don't understand how it starts making that noise after the lsd is installed, for multiple people... why would that amplify an already existing sound? Maybe i should have a mechanic check all of those components, maybe will find my problem? I love the performance of the lsd, but the thump is pretty embarrassing coming from such an expensive car.

[Offset Motorwerks]

Originally Posted by stephenf121

I just don't understand how it starts making that noise after the lsd is installed

Originally Posted by stephenf121

my car has a differential locking brace and polyurethane bushings

I always recommend upgraded differential bushings when we install an LSD. It could be that there was always a mild "thump" that now seems much worse because more noise transfers into the cabin?

[stephenf121]

offset motorwerks, is there a special soft bushing that could go on the lsd to take away some thump? If so which ones and what kind would you recommend?

[Joey911]

Originally Posted by stephenf121

offset motorwerks, is there a special soft bushing that could go on the lsd to take away some thump? If so which ones and what kind would you recommend?

Doubt you want soft bushing when you're looking for the performance of a LSD lol