Diffsonline E30 Racing Differential (325i & M3)
$1,499.00
Premium racing limited slip differential for your 6 cylinder and M3 E30. Choose your gear ratio and limited slip.
Diffsonline builds a wide variety of BMW differentials in house to accommodate the several different differential housings used in modern BMW’s. They start by cleaning the differential housing, then select the industry’s finest ring and pinion gears, apply the desired clutch packs and options, and finally carefully assemble the housing to be shipped to your door.
Custom built to your specification, the Diffsonline Racing Differential is the best performing diff you can put in your car. Multiple options in gear ratio and limited slip units available.
Limited Slip Options:
Diffsonline 3-clutch option: This is a BMW limited slip carrier with a third clutch pack. The unit is set to 40% static lock unless a different amount is requested by the customer, and it utilizes the stock ramp angles of 45/45 (acceleration/deceleration). This limited slip differential is much more durable than the factory M Variable unit and is well-suited for street and heavy track use. We recommend using Redline 75W110 gear oil for this application.
Diffsonline 3-clutch option with 30/90 ramps: This is a BMW limited slip carrier with 3 clutch packs and ramp angles which are modified from stock. The unit is set to 40% static lock unless a different amount is requested by the customer, and it uses ramps which are modified to 30/90 (acceleration/deceleration). This limited slip differential is much more durable than the factory M Variable unit and is well-suited for street and race use. Other ramp angles are available by request. We recommend using Redline 75W110 gear oil for this application.
Diffsonline 3-clutch option with 35/60 ramps: This is a BMW limited slip carrier with 3 clutch packs and ramp angles which are modified from stock. The unit is set to 40% static lock unless a different amount is requested by the customer, and it uses ramps which are modified to 35/60 (acceleration/deceleration). This limited slip differential is much more durable than the factory M Variable unit and is well-suited for street and race use. Other ramp angles are available by request. We recommend using Redline 75W110 gear oil for this application.
Diffsonline 4-clutch option with 35/60 ramps: This is a BMW limited slip carrier with 4 clutch packs and ramp angles which are modified from stock. The unit is set to 40% static lock unless a different amount is requested by the customer, and it uses ramps which are modified to 35/60 (acceleration/deceleration). This limited slip differential is much more durable than the factory M Variable unit and is well-suited for street and race use. Other ramp angles are available by request. We recommend using Redline 75W110 gear oil for this application.
Diffsonline Compact (medium) Race Carrier: This unit weighs in at just 14 pounds while other options weigh 22 pounds or more; the lower reciprocating mass helps to give you a competitive edge over the competition. This unit uses 6 clutches and single-driven ramps; making it the best working and most tunable limited slip on the market. The preload is controlled by coil springs so that preload is not lost as the unit wears. Since this is a Diffsonline exclusive product, we offer custom tuning assistance for your race team, and we can also cut any ramp and set preload anywhere you wish. We have a great baseline setting which covers 95% of cars running normal suspension setups. We recommend Redline 75W110, Motul Comp FF, or Castrol SAF-XJ fluid for this differential. NOTE: Please contact us for your specific requirements on this unit.
This unit is a race carrier and is recommended for race/track applications only, and this is the go-to unit for BMW’s running ST in Grand Am (E82, E90 or F30), and in any serious race environment. Many podium finishes have also been achieved in World Challenge by cars utilizing this setup.
$900 LSD core charge will be refunded upon receipt of your rebuildable core*. Core MUST be received within two weeks of delivery of replacement unit! If an open differential core is returned, only $200 will be credited.
*The ability to rebuild the returned differential will be decided by the differential builder.
Place a printed copy of your invoice in the box and return core to:
Diffsonline LLC
ATTN: MSW Core Return
190R Main St Unit 1
Wilmington, MA 01887
REM is a registered trademark of REM Chemicals Inc. registered in the U.S. Patent and Trademark Office.
BMW Fitments:
E30 M3, 325e, 325i
Differential Break-In Instructions
Fill your differential with the recommended fluid as described above. We recommend Red Line, Motul, and factory Castrol SAF XJ fluids for most differentials, but the OS Giken and Kaaz limited slip units require their own thicker fluid for proper operation. If you are experiencing chattering in your differential while cornering, you can add a limited slip additive from Red Line or GM. If you have a question about your specific application, email us, and we will get back to you with a recommendation.
All differentials built by Diffsonline LLC require a 1,200-mile break-in period. During this period, you should keep constant vehicle speeds under 80 mph and drive the vehicle moderately. This will allow the gears, bearings and limited slip parts to break in properly and without excessive heat. After 1,200 miles the fluid should be changed in your new differential with the same recommended fluid. After the initial flush, we recommend changing the fluid every 24K miles in a street driven car, or every 12K miles in a car that sees autocross and track day use.
For racing applications, one day of track use is recommended for break-in. Change the differential fluid after the one-day break-in procedure using the same recommended fluid. We recommend changing the differential fluid every other time you change the engine oil, or whenever the differential has gotten extremely warm.
Note: The differential fluid lubricates the ring and pinion gears, which transfer power from the driveshaft to the axles. The limited-slip unit requires fluid to keep all of the internal parts healthy and moving properly. Differential fluid changes areas imperative as changing the oil in the engine, and for the exact same reasons. Metal-to-metal contact wears down surfaces and creates heat from friction, which weakens parts and can lead to failure.
Normal Operations
During initial break-in, it is not uncommon for the rear end to have some chatter in the form of tire scrubbing or internal LSD noise depending on the vehicles limited slip choice. It is normal for some freshly rebuilt differentials to have a tight spot while turning by hand before break-in, as differentials are assembled and shipped dry except for some oil on the clutches and bearings during assembly. These conditions remedy themselves upon fluid fill and break-in process. Differentials with high levels of preload have difficulties unlocking depending on driving surfaces, such as rain, snow, gravel, etc.
| Series | Chassis | Model | Engine |
|---|---|---|---|
| Series | Chassis | Model | Engine |
| 3-Series | E30 | 325e | M20B27 2.7L I6 |
| 3-Series | E30 | 325i | M20B25 2.5L I6 |
| 3-Series | E30 | M3 | S14B23 2.3L I4 |
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