F22 M235i/M240i 6MT Diffsonline Custom Performance Differential

Increase the torque and traction delivered to the ground for faster acceleration and reduced lap times!

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$1,449.00 – $6,449.00

A great upgrade for drivers looking for added acceleration and grip for their M235i/M240i!

A differential upgrade/rebuild for your F22 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 curiously left the M235i/M240i with just electronic traction control to regulate wheel spin. The 35i/40i 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 M235i/M240i there are two factors to consider: limited slip type and gearing choice.


M235iM240i Limited Slip Options

DOL Helical limited slip
There are a number of limited-slip carrier upgrades for the M235i/M240i but they fall into two groups - clutch and helical. For purely street use we would recommend a helical such as Wavetrac or the in-house Diffsonline carrier. Helical diffs offer advantages in wear resistance and performance over traditional clutches. Torque transfer happens instantly and it doesn't need to sense a spinning wheel first. Lock-up is quicker and smoother and it's less affected by heat than a clutch. The only downside is potentially higher gear whine (but not in all cases). Some street 2 and 3-disc street clutch options have been discontinued due to the dwindling supply of original BMW cores.

Our clutch options are designed around serious track or race use since they can be easily customized around car setup and driving style. These diffs feature multiple clutch and spring discs - more clutches equal greater capacity for torque and heat management. Custom ramp angles are machined into the carrier to dictate lockup behavior under acceleration and deceleration (coast). Lower values equal a more aggressive lock-up. Our clutch options are generally not for street use except in highly-modified cars that need the extra traction.

The OS Giken is a multi-clutch design that is recommended only for track use and no warranty is provided.

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

Polished Ring & Pinion
The M235i/M240i manual transmission models came stock with a 3.08 gear ratio*. This is a good mix of acceleration and highway cruising (fuel economy and low revs). Shorter gearing (faster acceleration) may not be a factor in your decision as the biggest benefits to a F22 diff upgrade is with the limited-slip. Launching a tuned M235i?M240i 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 112 (3rd) and 147mph (4th) so a taller gear may avoid an extra shift. Refer to the 335i charts below for helpful speed and RPM data (data includes M235i gear ratios and other options).

* - all of the data we have shows 3.08 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

Diff REM Polish
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

Diff Core
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 M235i diff is $1,000, which is not included in the price and will be charged separately at the time of processing. Click here for the core policy and instructions. 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

BMW Diff Rebuilding
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 Series
F22 / F23 (2014-2016) > M235i 6MT
F22 / F23 (2016-2021) > M240i 6MT
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