A great upgrade for drivers looking for added acceleration and grip for their 228i/230i, 328i/330i, and 428i/430i!
A differential upgrade/rebuild for your F22/F3X 28i delivers performance far above the original factory spec. Diffsonline has 20 years of expertise in BMW differential upgrades and rebuilding. Only M models received limited-slip differentials which left the 228i/328i/428i with just electronic traction control to regulate wheel spin. The 28i/30i models becomes much more capable and usable performance cars with a proper limited-slip diff, especially when tuned for more power. Diffsonline specializes in BMW differentials and makes it easy to replace and upgrade your diff.
When planning a diff upgrade in your 228i/328i/428i there are two factors to consider: limited slip type and gearing choice.
228i/328i/428i Limited Slip Options
There are a number of limited slip options for the F22/F3X but they fall into two groups - clutch and helical. A traditional BMW M limited slip uses a clutch layout; the M2/M3/M4 use a viscous M Variable which we're not big fans of. Clutches are simple, reliable, and the less expensive. A traditional 2-clutch layout is fine for daily driving and moderate street use. We also offer a heavy-duty 3-clutch and a 3-clutch with more advanced ramp angles to change lock-up behavior on acceleration and deceleration. The OS Giken is a multiplate design that is recommended only for track use and no warranty is provided.
Several non-clutch type LSDs are also available. Wavetrac and Quaife both make a helical-style LSD that are more expensive but offer advantages in wear resistance and performance. Helical diffs use multiple sets of gears instead of clutch discs and plates. They are always engaged and have quicker and smoother response and are less affected by heat than a conventional clutch. There are a few downsides to helical diffs: if one wheel becomes airborne (hopping a curb on track or lifting the inside wheel during cornering) the lockup goes away. There is also additional upfront cost and some slightly higher gear whine than a traditional clutch LSD.
An open diff option is available for someone who does not want a limited-slip but wants a new gear ratio (or stock rebuild).
Gear Ratio
The 28i/30i manual transmission models came stock with a very short 3.91 final drive* and gearing may not be a factor in your decision as the biggest benefits to a F22/F30/F32 diff upgrade is with the limited-slip. Launching a tuned 228i/328i/428i can be difficult enough on stock gears so having a taller gear actually has many benefits. Another factor to consider is trap speeds in 1/4 mile drag races since gearing affects your speed in each gear. Stock gears top out at 106 (3rd) and 138mph (4th) so a taller gear may avoid an extra shift. Refer to the charts below for helpful speed and RPM data.
* - all of the data we have shows 3.91 as the only gear ratio for manual transmission cars. However, we have heard of cars not matching the factory spec. We may ask that you check your existing gear ratio before processing your order.
REM Polishing
REM treatment is a multi-step light surface polish of the gears and/or bearings that removes small imperfections and high spots on the surface. BMW does some final detailing on their ring & pinion sets that removes most of these imperfections but there is still room for improvement. High spots create heat risers which raise the surface temp of the surrounding metal and leads to imperfections and wear. REM polishing reduces internal temps and friction, improving performance and efficiency. It also makes the ring & pinion quieter with smoother engagement. REM polishing is done on a as-ordered basis and may result in additional build time. REM is a registered trademark of REM Chemicals, Inc.
Core Charge
We're able to offer rebuilt and performance differentials at a reasonable cost due to the use of cores. A "core" is your original used differential that is returned to our diff builder to be recycled into a new, fully-rebuilt diff. If we did not have cores available, and had to buy new factory differentials from BMW, our performance diffs would be four times the price they are now. To keep this upgrade feasible for the entire enthusiast community we rely on having your good, reusable core returned to the diff builder (Diffsonline) within fourteen days of receipt of your new diff. In order to cover the cost of sourcing another used diff, a core charge is applied to your order at the time of processing. This core charge can be refunded when you send back your original
limited-slip diff. Only complete and reusable cores will be eligible for a refund (no blown out, abused, or modified cores please). You must return a diff equal in components and accessories to the one sent to you. Non-limited slip (open) differentials returned for cores will not receive a full refund.
The core charge on a 28i/30i diff is
$400, which is not included in the price and will be
charged separately at the time of processing. You can also avoid the core charge altogether by sending in your original diff to be rebuilt. Note that this will mean downtime for your vehicle, so we recommended using the core service.
Rebuild Process
While we take in used diffs as cores, what you get is a fully rebuilt and properly set up unit that is often better than what BMW can provide. There is a lot of specialty knowledge required in the diff building industry and Diffsonline has over 20 years of experience in BMW differentials. Nearly all of the major retailers of performance differentials use Diffsonline, even when sold under other brand names.
Rebuilding a diff is a very involved process -
- The used diff is disassembled and cleaned
- The outside case (carrier) is stripped of grease, grime, and rust
- The desired limited slip unit is prepped
- The specified gear set is assembled with the LSD
- Any machining of the carrier is done in-house
- New OEM bearings are fitted
- New OEM seals are fitted
- The entire internal assembly is aligned (crucial in avoiding gear whine later on)
- Final assembly and checks
- Carrier is given a fresh coat of black paint
- Shipment to your door in special heavy-duty packaging
The packaging can be reused to send back your core. Diffs are shipped without covers and with no fluid inside. Diffsonline recommends Red Line 75/110 fluid for all of their differentials, except M Variable (Castrol SAF-XJ) and OS Giken (OS 80W250).
BimmerWorld offers FREE GROUND SHIPPING on all diffs.Upgrading the differential in your BMW is one of the best ways to improve handling, acceleration, and all-around performance. Whether you're looking to alter the final drive gear ratio, or add limited-slip functionality to get all that power to the ground in the turns, we've got the knowledge to guide you in the right direction. Should you have any questions on BMW diff upgrades or the process, please call or email one of our knowledgeable sales reps.
BMW Fitments: 2 SeriesF22 / F23 (2014+) > 228i
F22 / F23 (2014+) > 230i
3 SeriesF30 / F31 / F34 (2012+) > 320i
F30 / F31 / F34 (2012+) > 328i
F30 / F31 / F34 (2012+) > 330i
4 SeriesF32 / F33 / F36 (2014+) > 428i
F32 / F33 / F36 (2014+) > 430i
