[nwn54]

My mechanic just installed 034 engine and trans mounts, m3 rear subframe bushings, MFactory solid rubber rear diff bushings, and the MFactory helical LSD. My car is a 2007 automatic. I am experiencing some hard backlash/"clunking" in the rear when the car downshifts from 3 to 2, and 2 to 1 sometimes(it's not consistent). It also will transmit some serious backlash through the drivetrain on start up when parked on an incline, or when I have to turn hard to get into a tight space in a parking lot. The backlash was set upon install by my mechanic and is on the tighter side of factory BMW tolerances.
I expected more vibration/noise/drivetrain input, but sometimes it's pretty harsh with the "clunk". I would like to hear others added noise/backlash experiences when installing LSD and more intense rear diff bushings.
Thanks in advance.

[nwn54]

To add, I also have a Vwetish diff lock down kit installed. And, I have spoken to MFactory about it. Their customer service is top notch as far as I am concerned.

[Gohan335i7]

Getting mine installed in 1 week or so, I'll tell yah if there is any clunking , however I am not sure that is related to the LSD. At the least, I hope not...

[nwn54]

Originally Posted by Gohan335i7

Getting mine installed in 1 week or so, I'll tell yah if there is any clunking , however I am not sure that is related to the LSD. At the least, I hope not...

Let me know your experience after the install. To be clear, I don't think there is anything wrong with the diff or bushings. I am asking people who have done all of the upgrades that I just had completed how their car feels in and out of gear at low speed and sounds, etc. How different is it from oem? I know everyone loves the handling, launching, all around performance after the LSD install. I am with you all.

[limitdown]

Did mFactory build the diff for you? If not, maybe the builder didn't have the proper tools to set the correct backlash.
I have an Aug 2007 335i 6AT with your same bushing setup. mFactory built my large pumpkin, and it's been flawless for me.
Yes, their customer service is very good and very responsive.
I recently bought their sport axles/half-shafts.
When their center driveshaft begins production, I'll be buying that.

[nwn54]

Originally Posted by limitdown

Did mFactory build the diff for you? If not, maybe the builder didn't have the proper tools to set the correct backlash.
I have an Aug 2007 335i 6AT with your same bushing setup. mFactory built my large pumpkin, and it's been flawless for me.
Yes, their customer service is very good and very responsive.
I recently bought their sport axles/half-shafts.
When their center driveshaft begins production, I'll be buying that.

Thanks for the response. My mechanic installed it and the backlash is set within BMW spec. On the tighter side. A little less backlash than the factory diff had. The diff is functioning properly with no whine. Did you notice any added drivetrain noise/feel in the car?

[limitdown]

Many people report more noise with helical gear diffs, but I honestly don't hear any difference vs the factory diff. Maybe the noise has always been drowned out by my catless downpipes.
For your clunking noise, maybe your driveshaft wasn't reassembled at the exact original balance point. A shop I used before didn't mark the balance point before disassembling. The shaft wobbled and accelerating from a standstill felt like I was going over rumble strips.
It might also be a worn guibo or a worn center support bearing.

[twosickz]

Originally Posted by nwn54

Thanks for the response. My mechanic installed it and the backlash is set within BMW spec. On the tighter side. A little less backlash than the factory diff had. The diff is functioning properly with no whine. Did you notice any added drivetrain noise/feel in the car?

Ive had my mfactory lsd installed for 2 years now, single turbo and its worked flawless since day 1. No weird noises or clunks. Put together by mfactory though.

[nwn54]

Originally Posted by twosickz

Ive had my mfactory lsd installed for 2 years now, single turbo and its worked flawless since day 1. No weird noises or clunks. Put together by mfactory though.

Thanks. My car always clunked a little in the rear when you first pushed the start button after sitting for a bit. I asked the dealership about it years ago and they said they thought it was normal drivetrain noise/feel. We checked a few cars in the lot with the 6AT and they did it too. It's minor when it is oem. Now with the newly installed parts, it's more intense.

[Velocity26]

I wanted to do my upgrade one step at a time, so that I would know the effect of each upgrade, precisely to eliminate your problem.

I installed an M-Factory built pumpkin into my otherwise stock drivetrain and it sounds and acts just like stock. No extra "clunks" or vibrations to report. Other than some slight tire chirping when making tight turns under throttle, you cannot tell that the diff is not a stock open unit. I am betting that the stock bushings absorbed a lot of the shock and noise that you currently hear and feel.

[Banana Clipper]

I thought hard downshifts could be attributed to bad GUIBO and/or trans mounts?

[nwn54]

Originally Posted by Banana Clipper

I thought hard downshifts could be attributed to bad GUIBO and/or trans mounts?

The trans isn't shifting harder than when stock, but I feel the shifts through the rear subframe/trunk now when it is a harder shift. All of the feel and sound is from the rear, not the trans or the driveline.

[nwn54]

Originally Posted by Velocity26

I wanted to do my upgrade one step at a time, so that I would know the effect of each upgrade, precisely to eliminate your problem.

I installed an M-Factory built pumpkin into my otherwise stock drivetrain and it sounds and acts just like stock. No extra "clunks" or vibrations to report. Other than some slight tire chirping when making tight turns under throttle, you cannot tell that the diff is not a stock open unit. I am betting that the stock bushings absorbed a lot of the shock and noise that you currently hear and feel.

Kind of what I am thinking. The stock ones were pretty soft.

[Sshec152]

I have my entire rear suspension done, all solid bushings and arms with an mfactory lsd as well. I set up the diff myself, and have done many before. I get occasional clunking as well, its normal. On s550 mustangs, when doing all of the rear suspension i will also hear occasional clunking without even touching the diff. The soft factory bushings elimate this noise, with solid bushings it is no longer absorbed.

[nwn54]

Originally Posted by Sshec152

I have my entire rear suspension done, all solid bushings and arms with an mfactory lsd as well. I set up the diff myself, and have done many before. I get occasional clunking as well, its normal. On s550 mustangs, when doing all of the rear suspension i will also hear occasional clunking without even touching the diff. The soft factory bushings elimate this noise, with solid bushings it is no longer absorbed.

Thanks for the input.

[DavidBBall13]

I have the same issue with my car but I don't have an aftermarket LSD. I installed poly subframe and diff bushings (with lockdown kit) and I still have the same clunking when shifting just like OP.

I've had many BMW's with poly bushings in the subframe and diff and non of them have felt like this.

[whyzee125]

Originally Posted by nwn54

My mechanic just installed 034 engine and trans mounts, m3 rear subframe bushings, MFactory solid rubber rear diff bushings, and the MFactory helical LSD. My car is a 2007 automatic. I am experiencing some hard backlash/"clunking" in the rear when the car downshifts from 3 to 2, and 2 to 1 sometimes(it's not consistent). It also will transmit some serious backlash through the drivetrain on start up when parked on an incline, or when I have to turn hard to get into a tight space in a parking lot. The backlash was set upon install by my mechanic and is on the tighter side of factory BMW tolerances.
I expected more vibration/noise/drivetrain input, but sometimes it's pretty harsh with the "clunk". I would like to hear others added noise/backlash experiences when installing LSD and more intense rear diff bushings.
Thanks in advance.

My car does the little clunk thing on startup too, definitely from the rear. Perhaps I have upgraded rear bushings as my car's never had any of the tracking straight issues people always complain about but I've always just thought it was normal.

[nwn54]

Originally Posted by DavidBBall13

I have the same issue with my car but I don't have an aftermarket LSD. I installed poly subframe and diff bushings (with lockdown kit) and I still have the same clunking when shifting just like OP.

I've had many BMW's with poly bushings in the subframe and diff and non of them have felt like this.

Thanks the input guys. I thought it was bushing or lock down kit related. You have eased my mind, and I am no longer looking for something amiss in the rear of my car. Back to just loving the diff and bushing/mount upgrades. I appreciate the responses.

[335e92tx]

see http://www.e90post.com/forums/showthread.php?t=1134692

[nwn54]

Originally Posted by 335e92tx

see http://www.e90post.com/forums/showthread.php?t=1134692

Thanks. Sounds like others have experienced the same thing. Most seem to think it's most likely from upgraded bushings/mounts as well. Not the diff

[danas]

Make sure the driveshaft center support bearing was preloaded when mounting it back in. Very few places talk about it but that's what cured it for me.
Have to push (preload) bearing towards the engine, that keeps driveshaft from banging in to diff when load changes.
Had Mfactory diff installed for 2 years now. After installation had bad clunking sound every time I upshifted or went in to reverse. After moving csb made shifting smooth and quiet.

[nwn54]

Originally Posted by danas

Make sure the driveshaft center support bearing was preloaded when mounting it back in. Very few places talk about it but that's what cured it for me.
Have to push (preload) bearing towards the engine, that keeps driveshaft from banging in to diff when load changes.
Had Mfactory diff installed for 2 years now. After installation had bad clunking sound every time I upshifted or went in to reverse. After moving csb made shifting smooth and quiet.

The CSB was not loosened/unbolted for the diff and subframe work. Do you think it would be worth pulling the exhaust and heat shield to check to see if it was improperly installed all along? I have had the car since 19k miles(100k now) and the CSB has never been touched.