Rear Subframe Refresh Project

[darren p.]

I'm in the process of building up a rear subframe. I'm installing solid subframe bushings, replacing the differential mounts with Power Flex Street PU, doing the spherical bearings for the trailing arms and the inner spring arm and also changing the 3 upper arms to the Ground Control adjustable arms.

I'm upgrading the rear end with 4.10 gears and an upgraded diff although, I'm still unsure weather to go with the OS Giken or the Drexler...leaning towards Drexler 6-puck but not sure I need something so beefy. Main reason I'm leaning towards the Drexler is the OS Giken has no warranty and diffs online won't warranty it either and that scares me a little...on such an expensive proposition. I'd rather spend the extra money for the more expensive diff and the piece of mind of the warranty but if its nothing to worry about, I think the OS Giken would be fine for my skill level. Anyone heard any problems with the OS Giken? I know Florian has issues with the OS Giken but again, my skill level being a factor may not really see those issues. What do you all think?

I'm upgrading the rear brakes as well and figure I'll change the wheel bearings for good measure.

Rear sway bar I'm undecided on, I guess I can change this later if I decide to but I guess now would be the time to do it unless its easy to do later after the subframe is installed?

The complete subframe I bought was low miles but out of a DCT car...I know the diff is different and not just due to the 3.15 R&P vs the 3.85 R&P as the drive shaft is longer on the DCT vs 6MT. I am planning to use the DCT as a core when I order my diff from diffsonline. I see the axles have different part numbers between 6MT and DCT but would they work to replace my axles if I'm 6MT?

I'm only getting started, I picked up the complete rear subframe in my S4 Avant (jack of all trades car!) 2 weeks ago and disassembled it last weekend and have some pics to share. I already have the solid subframe bushings and the Ground Control Arms, the Powerflex diff bushings, the spherical bearings for the trailing arms and inner spring arms are on the way. This is going to be a winter project and then hopefully I can install the new fully built subframe in the spring.

Any tips, tricks or advice on the project or any ideas of things I haven't thought of are welcome.

Thanks for reading!

[Redd]

I'm using OSG Spec S LSD and Iove it. Zero issues, really transforms the car and gives a lot more confidence to push. Not sure what Florian's deal is with the OSG but lots of people using it with no issues.

[amrazM]

Where did you see 6mt and dct use different rear axles? to my knowledge they are the same, my originally dct car has a 6mt diff using the original axles. realoem doesnt call out any difference in the axles, just "exchange" and new units.

[deansbimmer]

The driveshaft is specific to either DCT or 6MT due to differences in the transmission lengths. The dimensions of the differentials are the same either way.

The axles are the same between 6MT/DCT.

We install a lot of OS GIKEN differentials and have had great luck with both their precision during installation, and positive reports from drivers. These diffs require a set of shorter output shafts due to their internal construction. PN 33131214068 (or, since they're backordered, lathe cut the splines on yours to the correct length).

You asked me about Cerakote... We love Cerakote for a variety of finishes and it's highly preferred over powder coating due to its thin film, making it far less prone to cracking and chipping, or changing a precision part's external dimensions. For a subframe, it's difficult to Cerakote the entire assembly as the coating wants to flash before it's finished which can affect it's strength and visual qualities. We find that their air cured C-Series works great and can be easier for large items.

[911r]

I would say a Drexler GT Race from Florian is in a different class from an OSG .. not to say OSG is bad.

[darren p.]

Thanks all, I guess I just wasn't reading the part numbers correctly on the axels but it makes sense that the drive shafts are differenct based on the diffrence in length of transmissions.

Been busy with other stuff but finally got the 20-ton hydrolic press from HF and am going to get started on the subframe shortly.

Decided on the Drexler diff. I'm sure its overkill for me needs but maybe I will grow into it. Still need to decide on the ramp angles - 50/40‚ 40/50‚ 40/35 or 35/40...this is what I'm the least sure of but have been reading quite a bit and just don't want to make the wrong decision.

[m3s65b4.x]

I don't think Drexler is overkill, one of the best mod for e9x m3. Running 4 yrs GT Race Light 4.44 (max. lockup: 70% / 50% , ramps 50/60) on street, performs well in summer and winter.