[Dan_Q]

Car: 2011 335i 6MT Sedan: Wagner high flow downpipe, VRSF 7” FMIC, Cobb AP3 running Stage 2 performance (91 oct)

Rationale: I have the nicety of driving a stretch of twisty canyon road every day between my home and work. I wanted to get a limited slip diff because my car seems to immediately have DSC triggered if I try and accelerate while turning at all. It is a real buzz kill to only be able to use my engine’s power when going in a straight line. I looked into the Quaife and Wavetrac LSD options but I couldn’t justify their price. I have a welded ring gear and paying for a fully built pumpkin was going to be very expensive. The other option was just getting the differential unit and then cutting off the ring gear/drilling/tapping/ installing it all into my diff housing. That was not an option since this is my daily driver and I can’t afford multiple days of down time to do it. Plus I don’t have access to the facilities to do the work. I accepted that I would likely never replace the open diff. That was up until I saw the MFactory unit come out. Its pricepoint was significantly lower than the other options. When MFactory had a big sale come up a few months ago and I figured it was now or never. I elected for “now”. I had the options of changing the diff gearing for better acceleration but I stuck with the factory gearing so I wouldn't adversely affect the fuel economy.

Arrival: MFactory built me a pumpkin and had it in the mail in just a couple of days. I received it in a big box full of 1” thick cardboard chunks to keep it wedged in there during transit. The refurbished housing was pristine and could have passed as brand new. There were caps covering the holes where the half shafts would be inserted and the whole thing was bagged to prevent FOD from getting into the housing. The diff came with a new nut to attach the driveshaft. I picked up new half shaft bolts from Tishner and a quart of Royal Purple 75W-90 gear oil. Doubt I needed to replace the half shaft bolts but I got them anyway.

Install: I tried doing the install myself but failed. I got the exhaust and heat shields off but the wrench I had to loosen the nut connecting the driveshaft was too thick to fit on the nut and too long to actually turn the nut with the car only up on jack stands. I reinstalled everything and decided to take it to the pros (first repair I have ever paid for in my life!). I made an appointment at AR Designs and about 10 days later pulled in to have the diff installed. They let me hang out in the shop and assist some throughout the entire repair so I was able to see how it was done. I will say that lifting the new diff into place while threading the driveshaft on and lining up the half shafts is not a 1 person job. I’m pretty resourceful and I’m almost positive that I couldn’t have done it alone. Pretty much everything else with the install seemed straightforward. The one oddity was that the nut connecting the driveshaft to the diff input shaft was tight for multiple turns. I expected it to break loose and then be free running but it took quite a bit of muscle for about 3-4 revolutions before it loosened up.

Initial Impressions: I had been warned by another member about this particular diff clunking on his car when he shifted. So I had a bit of trepidation when I pulled out of the shop. I wasn’t sure if I had to break it in for a little bit so I played things safe and drove like a grandma for a couple of days. The car felt more or less identical to before I had the LSD installed.

Long Term Impressions: Between the diff, shipping, hardware and labor it came to about $1,800. I am still getting significant wheel spin when attempting to accelerate while turning and that was the main thing I was trying to improve. I’d say the increased amount of acceleration allowed before breaking traction is not much more than the open diff. For now I’m hoping it is due to still being on 8” wide winter tires. My expectation was that I would get immediate hook up with minimal (if any) wheelspin since my car does not have extreme levels of torque. Perhaps that was an unrealistic expectation or perhaps it is still possible once I install my wider summer tires. Other not so great news is that over the course of the first week it developed a clunk when shifting into 1st from a stop. Sometimes it isn’t there at all, sometimes it is minimal and sometimes it is very noticeable. When it is noticeable, there is also reluctance for the shifter to go into gear. The stock diff was always very smooth and never had this problem. It is isolated to going from 0 mph to 1st gear shift and it doesn’t happen when performing any other shifts though. The positives with this diff are that with DSC off the car will go into what feels like very controllable oversteer. Maybe this is more useful for people who track their cars but I can’t say I will use it very much since my car only sees public roads. So weighing the pros and cons against the cost, right now I’m going to say it wasn’t worth it to me. It hasn’t achieved my primary purpose (increased traction) and it had some negatives that came with it.

I will say that dealing with MFactory was great. They answered all my questions and the product arrived in perfect condition. Everything with them was hassle free. When I shipped back my core, they refunded me within 2 weeks. Plus they allow for a 30 day turnaround which was double what I saw elsewhere. They seemed amenable to extending the turnaround time further if I needed it. For the amount of work required to build up the new diff in a pumpkin I don’t understand how they can even make money off of the rebuild service. A huge portion of why their diff is such a deal is because the rebuild service is dirt cheap. I certainly can’t fault them on that.

Once I get my summer rubber on I’ll update this if I find that things have changed.

Update: Been too busy to be using the web for much more than toiling away at work so I utterly failed you with a timely update. Installation of the summer tires had a predictably massive difference. I can’t break traction in a straight line with them on and DSC intervention isn’t too severe when accelerating while turning. Controlled slides are quite easy to pull off. So performance wise the MFactory LSD delivered.

Buuuuut… the clunk is quite severe and I am fully annoyed with it. The car clunks with going into 1st from a stop quite strongly. It also clunks when upshifting to 2nd, 3rd, and 4th. It clunks when downshifting as well. And it is bad enough that when my wife drove my car recently she told me she thought she had broken something when shifting into 1st at the first stoplight. I didn't volunteer that that was a result of the $1,800 "upgrade" I voluntarily did to the car last spring.

Update: Later posters on this thread revealed that the clunk could be caused by insufficient preloading of the center support bearing of the driveshaft. i.e. installation error. This was apparently not something my mechanic was aware needed to be done. In light of that, I removed the exhaust and preloaded the bearing correctly and the clunk was minimized. There was cast off material (rubber? grease?) at the location of the center support bearing which leads me to believe that the bearing may have been damaged and that may be why there is still some clunking. It definitely improved quite a bit with this change though. I think that when I eventually do a clutch replacement I will likely replace that bearing and perhaps the clunk will be eliminated entirely. So I can't confirm the diff had nothing to do with the clunk in the first place but I suspect that it was entirely related to improper installation.

[mlifxs]

Thanks for the honest review. Hopefully things improve with the summer tires.

[Volasko]

Very detailed review, +1 for you!

[silver07335i]

Thanks for the review and will subscribe for future updates.

[ksalih]

Good honest review OP. Might I suggest replacing the oem rear subframe bushings with m3 or better ones? I think this will help you to your goal.

[raceyBMW]

Bummer that you haven't had the best experience so far, hopefully the traction issues will go away once you have your summer tires on.

I will say, mine developed a clunk at one point, I got back under there and found that some of the diff mounting bolts had worked loose slightly. So I red Loctited them and torqued them all back up and has been noise free to this day. Might be worth looking into, would be cheap assurance at least before you take the next step of removing.

OP, if you decide you want to go another route, I have a stock bolted ring gear diff. (full pumpkin) from my 2007 auto (3.46 final drive), that had about 42k miles on it before I took it out of my car and swapped for a full pumpkin with a Wavetrac LSD. Would part with it for a fair price since I wouldn't have to ship. This would reduce your downtime, but would have to weight whether you would want to change the final drive ratio from the one on the MT.

[davidwarren]

when you say wheel spin, are you talking about single wheel spin?

[ajsalida]

Nice review thanks for posting it. My understanding of adding a mechanical LSD to our cars, that already have the e-diff (brake actuated pseudo LSD), is it won't do much except under very high HP straight line runs, and maybe on powering out of corners or trail braking into them.

There has been some misinformation out there about how bad the e-diff actually is. From what I can tell on flat road straight line accel with no surface issues you'll never know the difference. Others chime in here if I'm wrong please. Witness many burn outs and double black lines people lay down on vids with no LSD added.

I think the issues an LSD cures is response time and the fact that you'll wear out rear pads very fast otherwise if you lean on the e-diff frequently. It also may be pretty subtle, for example turn in braking on a car with mechanical LSD is obviously different, I am not sure our cars e-diff will do so in the same manner, I have never felt it and I have tried (but I have an XI). Same for powering out of a corner.

But another thing is as far as I know you cannot turn off the e-diff. Ever. It is always on and only works under power, and only engages when it sense excessive wheelspin on one wheel inconsistent with other sensor data. Unlike a true LSD that will enforce some % max lock-up regardless. It does not get turned off with DTC on or with DSC full off. So a mechanical LSD is only going to do so much above and beyond the e-diff, and just ahead of the e-diff time-wise when it would have been engaged, or like off throttle trail braking into a corner where it will add some lock up to the inner wheel even without power, or I guess in situations where the programming is distinctly different from what a true LSD would do.

The point I am making is e9x never had a true open diff, ever. It has some strange pseudo LSD that isn't all that great but way better than a true open diff. So I would not expect a true LSD to feel all that much better unless your application is one of the above where it is needed. I happen to like the feel of a real LSD, it is the same and predictable on or off throttle, turning or not. Who knows WTF they programmed the e-diff to do. But this is important, now you'll have TWO LSD's, one mechanical one electronic, not sure if they'd ever work at cross purposes to one another.

In case you are wondering, LSD was the next thing on my list before RB's, so been thinking about this a lot. But I doubt my driving would require one unless I start doing a lot of track events again.

[Dan_Q]

Originally Posted by ksalih

Good honest review OP. Might I suggest replacing the oem rear subframe bushings with m3 or better ones? I think this will help you to your goal.

That is part of the plan for this summer.

Originally Posted by raceyBMW

I will say, mine developed a clunk at one point, I got back under there and found that some of the diff mounting bolts had worked loose slightly. So I red Loctited them and torqued them all back up and has been noise free to this day. Might be worth looking into, would be cheap assurance at least before you take the next step of removing.

OP, if you decide you want to go another route, I have a stock bolted ring gear diff. (full pumpkin) from my 2007 auto (3.46 final drive), that had about 42k miles on it before I took it out of my car and swapped for a full pumpkin with a Wavetrac LSD. Would part with it for a fair price since I wouldn't have to ship. This would reduce your downtime, but would have to weight whether you would want to change the final drive ratio from the one on the MT.

I have actually checked the mounting bolts. No luck there.

I actually saw you selling your pumpkin when I initially started looking at LSDs and considered it. It would have allowed me to do the swap myself much easier but ultimately I decided I didn't want to change the gearing.

Originally Posted by davidwarren

when you say wheel spin, are you talking about single wheel spin?

Yes I am talking about still spinning the inside rear wheel. I was under the impression that the LSD would be able to transfer enough of that torque to the outside wheel that I would essentially have no traction loss at all. Not the case. The affect is that DSC still triggers which causes the throttle to cut. Like I said, maybe my impression that this would not occur was unrealistic or maybe it is just because my winter tires don't have sufficient grip to increase the threshold enough for this not to happen.

ajsalida: I think you are on to something with your understanding. I probably should have done some more research into this but I didn't read many reviews that actually gave their impressions on the results that came with an LSD install. Or if people did have results, it happened with complete suspension overhauls and so there were 5 other factors at work at the same time. A couple of people said the LSD was their best mod period. Overall it left me with the impression that installing an LSD = lots more traction.

The one place where I would agree there is a big difference with the LSD is when driving with DSC off. When you do that you can bury the throttle mid corner and get controllable oversteer. That wasn't possible with the stock diff. Maybe that ability is good if you're tracking the car, if you want to impress your friends or if you want to get rid of excess rubber on your rear tires. But for me, I try to have a little fun on public roads but I want to keep all 4 wheels firmly planted on the pavement so that things stay safe for myself and my fellow motorists. I am not a super skilled driver with training on how to handle the car at its limits, so I keep DSC on over 99% of the time and thus oversteer isn't something I'm able to take much advantage of. If more grip is all I am after, I may have been better off getting an xi. Ironically one of the reasons I didn't get an xi is because they aren't available with the sport suspension. But now I have plans to replace my entire suspension anyway.

[MFactory]

When you start to spin, are you lifting off the gas to try to compensate? With a Torsen style LSD, the more throttle you apply, the more effective it is.

[Dan_Q]

Originally Posted by MFactory

When you start to spin, are you lifting off the gas to try to compensate? With a Torsen style LSD, the more throttle you apply, the more effective it is.

Yes I believe that I usually do although I don't understand why that would impact the behavior I'm experiencing. By the time I am lifting off the throttle the DSC has already kicked in and the throttle has been reduced anyway.

I will read your differential sticky and see if I can educate myself more on their operation though. It would certainly be nice if my perceived shortfalls could be attributed to user error.

[litxus]

Hm, your review put a question mark in my future plans for LSD? I really hoped that LSD prevents too much of single wheel spin, kind of when waiting to pull into a busy street. Are you saying it is same as stock, even if you click traction control button once? My main issue is that it cuts power way too much, when trying to move out of a turn or starting out.

[MFactory]

Originally Posted by Dan_Q

Yes I believe that I usually do although I don't understand why that would impact the behavior I'm experiencing. By the time I am lifting off the throttle the DSC has already kicked in and the throttle has been reduced anyway.

I will read your differential sticky and see if I can educate myself more on their operation though. It would certainly be nice if my perceived shortfalls could be attributed to user error.

If your traction control is kicking in before the LSD even gets a chance to work effectively, you have some serious traction issues (be it chassis setup, tires, mounts etc). This is why you find the LSD working it's magic with the traction control turned off (i.e nothing to cut the throttle)

[nitehawk]

Having ran a wavetrac in the past on a similarly modded 6MT n54 335i, I can tell you that DSC intervention should be a lot less after LSD install. Wheelhop came along with LSD too. So the way the car launched from a dig was rather unique. With that said, LSD doesn't replace the need for quality tires. I hope its just your winters and you have a good summer set?

[Dan_Q]

Originally Posted by litxus

I really hoped that LSD prevents too much of single wheel spin, kind of when waiting to pull into a busy street.

I can't really comment on pulling out into traffic yet. There is still so much sand on the roads at intersections that I think I'd be slipping regardless of if I had an LSD or not for a few more weeks. The two places I am still getting DSC intervention are 90° turns when applying throttle or fast sweepers when applying throttle.

Originally Posted by MFactory

If your traction control is kicking in before the LSD even gets a chance to work effectively, you have some serious traction issues (be it chassis setup, tires, mounts etc). This is why you find the LSD working it's magic with the traction control turned off (i.e nothing to cut the throttle)

The only thing that I think could be contributing to this are the 225 width winter rear tires. The suspension is the stock sport suspension with 40k miles on the clock and the alignment was done last fall when I put the winter rubber on.

Originally Posted by nitehawk

Having ran a wavetrac in the past on a similarly modded 6MT n54 335i, I can tell you that DSC intervention should be a lot less after LSD install. Wheelhop came along with LSD too. So the way the car launched from a dig was rather unique. With that said, LSD doesn't replace the need for quality tires. I hope its just your winters and you have a good summer set?

That is promising to hear. I'm waiting for summer wheels to show up which have been on backorder for over about 6 weeks. Hopefully last weekend was the last snowstorm for the season and I'll actually be able to install them when they show up.

[litxus]

How is LSD with some slip (clicking traction control once, traction not fully off)? As I use this quite often when it is slippery, as it gets moving faster, but you still have to watch your throttle.

[Dan_Q]

Originally Posted by litxus

How is LSD with some slip (clicking traction control once, traction not fully off)?

It appears that this is the state in which a LSD is designed to operate in.

[raceyBMW]

Originally Posted by ajsalida

Nice review thanks for posting it. My understanding of adding a mechanical LSD to our cars, that already have the e-diff (brake actuated pseudo LSD), is it won't do much except under very high HP straight line runs, and maybe on powering out of corners or trail braking into them.

There has been some misinformation out there about how bad the e-diff actually is. From what I can tell on flat road straight line accel with no surface issues you'll never know the difference. Others chime in here if I'm wrong please. Witness many burn outs and double black lines people lay down on vids with no LSD added.

I think the issues an LSD cures is response time and the fact that you'll wear out rear pads very fast otherwise if you lean on the e-diff frequently. It also may be pretty subtle, for example turn in braking on a car with mechanical LSD is obviously different, I am not sure our cars e-diff will do so in the same manner, I have never felt it and I have tried (but I have an XI). Same for powering out of a corner.

But another thing is as far as I know you cannot turn off the e-diff. Ever. It is always on and only works under power, and only engages when it sense excessive wheelspin on one wheel inconsistent with other sensor data. Unlike a true LSD that will enforce some % max lock-up regardless. It does not get turned off with DTC on or with DSC full off. So a mechanical LSD is only going to do so much above and beyond the e-diff, and just ahead of the e-diff time-wise when it would have been engaged, or like off throttle trail braking into a corner where it will add some lock up to the inner wheel even without power, or I guess in situations where the programming is distinctly different from what a true LSD would do.

The point I am making is e9x never had a true open diff, ever. It has some strange pseudo LSD that isn't all that great but way better than a true open diff. So I would not expect a true LSD to feel all that much better unless your application is one of the above where it is needed. I happen to like the feel of a real LSD, it is the same and predictable on or off throttle, turning or not. Who knows WTF they programmed the e-diff to do. But this is important, now you'll have TWO LSD's, one mechanical one electronic, not sure if they'd ever work at cross purposes to one another.

In case you are wondering, LSD was the next thing on my list before RB's, so been thinking about this a lot. But I doubt my driving would require one unless I start doing a lot of track events again.

Not actually completely true on the e-LSD comment that all E9x have it, I believe the MSD80 early build 335's did not have it (for instance my manual has no mention of the "e-diff"). Rest of your comments are spot on though.

If you have it, the simulated "e-LSD" will always be activate, even if you turn off all other traction aids.

http://www.bmw.com/com/en/insights/t...erential_brake

[ajsalida]

Originally Posted by raceyBMW

Not actually completely true on the e-LSD comment that all E9x have it, I believe the MSD80 early build 335's did not have it (for instance my manual has no mention of the "e-diff"). Rest of your comments are spot on though.

If you have it, the simulated "e-LSD" will always be activate, even if you turn off all other traction aids.

http://www.bmw.com/com/en/insights/t...erential_brake

Yeah I have read a lot of conflicting info on this topic and I am not really sure what is 100% correct. The clearest explanation I found was that all 2006-on e9x cars have e-diff, but in mid 08 there was a change in the software. Prior to the change, the e-diff was turned off when DTC/DSC was full off. So that DSC off (triangle with circle) meant all electronic controls except ABS brakes were off. Starting in mid 08 on, DSC full off kept the e-diff on, so that in those cars there was no way to turn it off. There was some discussion I read (it has been a while) that it could be coded off in those cars but I never pursued it.

There is some more detailed discussion over on 1addicts forum, a guy did some track data acq showing e-diff clearly working on earlier cars.

The bottom line is I think it is very likely with 08.5 and earlier car you can turn it completely off and have a true open diff, ie e-diff is bundled with DSC/DTC. These cars when you add a mechanical LSD you get a true uninhibited LSD but only with DSC full off. 08.5 and later unfortunately you get the two types working with/against each other even with DSC full off, e-diff is stand-alone and cannot be shut down. There are various scenarios you can imagine where e-diff and LSD would interfere with the other.

The fact that there was this fundamental but little-known software change mid 08 may be why there is so much confusion surrounding the e-diff and LSD's on e9x cars in general.

[Gennosuke]

Hey DanQ,


Thanks for the review.

Any updates with your summer tires on?

Computer intervening is most likely your winter tires.

I also recently had installed the MFactory LSD on my car this past winter. I opted for the 3.46 gearing.

I had it installed right after I put my winter tires on....225/40R-18 Michelin X-Ice Xi3 XL.

And I had very similar experience where the computer intervenes more frequently when accelerating hard and I figured it was the studded winter tires. I'm FBO. And for suspension...m3bits front and rear arms...m3 subframe bushings...stock sway bars....coilovers...Megan toe arms...defiv kit.

The car def perform a lot better during snowy conditions with DTC pressed ON because like you and everyone said it's because the LSD is doing it's work.

I recently put my PSS and summer wheels back on and the computer doesn't intervene like it would when I didn't have the LSD in the car.

[Dan_Q]

Originally Posted by Gennosuke

Any updates with your summer tires on?

Computer intervening is most likely your winter tires.

I also recently had installed the MFactory LSD on my car this past winter. I opted for the 3.46 gearing.

I had it installed right after I put my winter tires on....225/40R-18 Michelin X-Ice Xi3 XL.

And I had very similar experience where the computer intervenes more frequently when accelerating hard and I figured it was the studded winter tires.

The car def perform a lot better during snowy conditions with DTC pressed ON because like you and everyone said it's because the LSD is doing it's work.

I recently put my PSS and summer wheels back on and the computer doesn't intervene like it would when I didn't have the LSD in the car.

That is good to hear. I've also got X-Ice 3 tires with a 225 square setup. The summer rubber should hopefully be on by next weekend. That is, if the summer wheels that have had delay after delay after delay actually did get shipped out yesterday. And I thought I was being proactive by ordering them in February! I was hoping to get Michelin PSS summer tires but they were out of stock in 265's so I opted to get Conti Extreme Contact DW's since I don't feel like waiting around till June for them to arrive. I'll post back with an update later but good to hear your experience has been good.

[turo]

Dan_Q please keep us updated when you get the summer tires on. I'm thinking of doing this mod next.