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      12-22-2012, 01:40 PM   #1
DallasBoosted
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Drives: '08 E92 335i
Join Date: Apr 2012
Location: Dallas

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2008 BMW 335i  [5.00]
OS Giken LSD, Powerflex Diff and Subframe Bushings, and UUC Swaybars Installed

My current setup:

Ground Control Street/School Kit
  • 525f/650r springs
  • Koni Single adjustables
  • GC Camber Plates

M3 control arms front and rear; Front wishbones and tension links, Rear M3 camber arms.

Ground Control Toe Arms

I also have Apex Arc-8's 18x8.5 and 18x9.5 with 245/275 Michelin PSS's, and a stoptech BBK in the front.

So I knew I needed an LSD, but I decided to do the suspension first. Now that thats out of the way, I knew I'd be shopping.

As most of you know, the rear subframe bushings are a weak point. These bushings are pitiful. Here's what the M3 bushing looks like next to the 335i bushing (335i bushing on the right):



So you know thats got to go. I decided on the powerflex subframe bushings. I know a lot of people have gone with the m3 bushings and those are probably good pieces as well, but I wanted to give these a try as rubber bushings in such a critical part didn't seem like a great idea to me. I was also considering the turner solid aluminum bushings, but was talked out of it due to NVH. I think they'd probably be fine. Anyway, I went with the powerflex yellows.



As many of you have experienced as well, when you accelerate hard in a lower gear and the car breaks traction, the rear end attempts to change lanes to the left. Always fun on 2-lane roads with oncoming traffic. I decided to do the powerflex diff bushings as well to help lock down the diff and keep the driveline pointed where it is supposed to be pointed.



Since you have to more or less drop the subframe to do the subframe bushings and you also have to drop the subframe to do the rear swaybar, I decided to do swaybars at this time as well. I got a set of UUC swaybars from a forum member. They are 27mm front and 19mm rear bars. They both have 2-hole adjustments, I left them both on the softer adjustment.



Since I bought this car to be my street/track vehicle, and since getting the power this car can make to the ground will be its major strong point, I decided to not compromise on the differential. It was apparent from the first time I drove the car with the traction control off that it needed an LSD; the question is just which one, and who are you going to buy it from.

The quaife and wavetrac LSD's are great units, and certainly a tremendous improvement over the open diff. I wanted something a little less open, something that gets closer to 100% locking to really get the power down. The choice was going to be between a diffsonline 2-3 clutch unit or the OS Giken. When I saw VAC was running a sale on the OS Giken units, my choice was made for me.



The guys at VAC were very helpful and if you haven't seen their process for what goes into making a 335i (welded) differential, you need to check it out: http://www.vacmotorsports.com/blog/v...-how-we-do-it/ These guys are pros. You can't go wrong getting your stuff here.

After discussing the issue with the guys at Vorshlag and VAC, I decided to leave the settings on the OS Giken diff the way it comes from Giken. In this configuration it progressively locks at a very controllable rate, and does (according to Giken) reach 100% locking.

I'm also lucky in that I live near one of the best BMW suspension shops in the country, Vorshlag Motorsports. These guys are famous for their LS1 swaps into E30's and E36's, but basically they are just a good bunch of guys that are into racing and cars and run a shop to support what they like to do. This is the best kind of place to get your work done because they aren't just pushing production and numbers, they are actually interested in their work and race on the weekends in addition to building customers cars during the week. It's a win/win.

So I had the diff delivered to Vorshlag and brought the sways and got the install started. I dropped by to check on progress and snapped this pic of my subframe totally out of the car:



They had the tools necessary to get the stock bushings out in a timely fashion. The powerflex bushings are a perfect fit and have a cool yellow color. Also you see the swaybar that runs along the top of the subframe and you understand why that sucker is so hard to install with the subframe on the car.

The OS Giken diff from VAC waiting to be installed:



I had to go home and earn money to pay for all this crap so I came back the next day.

Here's the OS Giken diff installed (and the subframe put back on the car):



Here's the diff bushings which are tough to see but make a big difference:



And you can see the rear diff bushing and some of my pretty rear suspension in this one:



So the big question is, how much difference did all this make? Is it worth it? None of this crap was cheap and it was a lot of work to install.

Yes. The entire rear end of the car is transformed. Thats easy to say but not easy to describe; basically all of the bad traits of the stock rear end are gone.

The wobbly feeling of the rear end is gone. With 650lb springs and matching dampers it never felt floaty, but it didn't feel solid either. Thats gone. Its solid now.

The lane change on wheelspin is gone. The rear end will waver around a little bit when the wheels spin because it doesn't have any traction; but both wheels are spinning (verified ) and there is a ton of forward thrust on wheelspin where the car tended to sit still or not go forward much under wheelspin before.

Any wheelhop is gone. I didn't have much before but it just smoothly spins the tires now. I need to take out a life insurance policy on my rear PSS's.

The big change of course is the LSD. A quick comment on my power mods... I have FBO with no meth. Figure 370-390rhwp. I can floor it now going around a streetcorner in 1st gear and it'll spin a bit then hook. It is throwing you forward the whole time, and the wheelspin and oversteer is controllable. In 2nd gear the wheelspin is minimal unless you are on slippery pavement. In testing this out I did some pretty unintentional drifts that would probably have resulted in a spin with the open diff that were VERY controllable with the LSD. Freakin beautiful. The car feels a LOT faster in 2nd gear because the power actually goes to the ground.

The swaybars are noticeable; the car definitely corners with less body roll than it did previously. Its difficult to really test the limits on the street without being unsafe, so I'll just say these are noticeable and a good mod. I've read a lot on this board about "DONT DO THE REAR SWAYBAR ITLL TRY TO KILL YOU!" etc... this is nonsense. I haven't noticed any particular rear end instability yet, and I was driving around streetcorners full throttle for an hour last night.

A comment on NVH: hahaha. Come on. If there's any NVH increase, I can't detect it. Any of you worried about this, take the panties off and give them back to your wife. I can't even notice any NVH much less making it "intolerable". Do these bushings. Totally worth it.

I have another track weekend coming up and will report on the result of the LSD/bushings/sways on the track after that.

Once again big thanks to the guys at VAC and Vorshlag.

Last edited by DallasBoosted; 12-22-2012 at 06:54 PM.