A great upgrade for drivers looking for added acceleration and grip for their E46 323i/325i/328i/330i!
A differential upgrade/rebuild for your E46 non-M 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 non-M E46 with just electronic traction control to regulate wheel spin. The E46 becomes a much more capable performance car with a proper limited-slip diff. Diffsonline specializes in BMW differentials and makes it easy to replace and upgrade your diff.
When planning a diff upgrade in your E46 there are two factors to consider: limited slip type and gearing choice.
E46 Limited Slip Options
There are a number of limited slip options for the E46 but they fall into two groups - clutch and helical. The traditional BMW M limited slip uses a clutch layout. Clutches are simple, reliable, and the less expensive. A traditional 2-clutch layout which is fine for daily driving and moderate street use. We also offer a heavy-duty 3-clutch or 4-clutch as well as 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.
Multiple gear options are available to meet your acceleration needs. There were multiple stock gear ratios available, from a super tall and fuel-efficient 2.93 up to a snappy 3.46. The 330i ZHP came with a shorter 3.07 to give it a little more punch. Shorter gears have a higher number and will deliver faster acceleration at the expense of top speed and comfort at highway speeds. The gear ratio you choose is based largely on personal preference and how you plan to use the car. A 3.46 will have much more acceleration around town but will put 80mph highway revs around 3,700 (5-speed) or 3,200 (6-speed). Keep in mind that shorter gearing requires more frequent shifting and you will be into the E46's low 6,500 RPM rev limit sooner (performance software with a higher rev limit is encouraged). Refer to the charts below for speed and RPM data.
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.
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 diff is returned with the same flanges it was supplied with. If you need different flanges - such as converting from auto to manual - you need to tell us which flanges to include.
The core charge on a E46 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.
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: 3 Series
E46 (99-05) > 323Ci
E46 (99-05) > 323i
E46 (99-05) > 325Ci
E46 (99-05) > 325i
E46 (99-05) > 325xi
E46 (99-05) > 328Ci
E46 (99-05) > 328i
E46 (99-05) > 330Ci
E46 (99-05) > 330i
E46 (99-05) > 330xi