E82 1M Diffsonline Custom Performance Differential

Better traction, handling, and acceleration - all in one upgrade!

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$1,449.00 – $9,848.00

A great upgrade for drivers looking for added acceleration and grip for their E82 1M!

A differential upgrade/rebuild for your 1M delivers performance far above the original factory spec. Diffsonline has 20 years of expertise in BMW differential upgrades and rebuilding. The factory M Variable viscous differential is good for about 60,000 miles before it's worn out. What good is a worn-out limited slip diff in an M car? Diffsonline specializes in BMW differentials and makes it easy to replace and upgrade your diff.

When planning a diff upgrade in your 1M there are two factors to consider: limited slip type and gearing choice. For a turbo M car like the 1M, limited slip choice is more important than gearing.

1M Limited Slip Options
Stock M Variable - The torque-sensitive, variable M differential identifies exactly when traction is needed. Even when wheel grip varies enormously, such as on bends taken at high speed, roadholding remains excellent as the locking power between the left and right rear wheels can be raised to 100%. But it has downsides as well: the internal viscous system needs rebuilding every 60-80,000 miles, and the viscous design is inconsistent. There is a small delay between the open diff action (driving in a straight line) and torque transfer (cornering, wheel spin) and because the system is variable the reaction and lock-up can be different from one corner to the next. Racers and dedicated track cars typically opt for one of the more reliable and simpler multi-clutch limited slip systems we offer.

2 Clutch - The traditional BMW limited-slip desgin that is simple, reliable, and the least expensive. A 2-clutch is what most BMW M cars had before the M Variable was introduced and is what we recommend for street use. Heat may become an issue on high horsepower cars or on the track and a 3 Clutch design will perform better.

3 Clutch - Same as the 2 Clutch but with an extra clutch disc. The 3 clutch unit is designed to further increase the locking abilities of the differential for more aggressive traction and grip. Great for street cars seeing numerous track days per year.

3 Clutch with Custom-Engaging Ramp Angles - Our best-selling carrier type. The carrier incorporates custom ramp angles built into the carrier for an engagement that is more substantial and track oriented. This unit offers excellent turn-in and the ability to lay down some serious power earlier during track-out. This unit has proved to greatly reduce track times and, as a result, has created some very happy customers!

Wavetrac - This design does not use clutch plates like a traditional limited slip diff. Wavetrac uses helical gears to transfer torque from one wheel to the other. The helical gear concept delivers smooth power delivery without a fixed lock-up like on clutch-type differentials (no push from the back end leading to understeer). Wavetrac operates seamlessly to the driver and traction control systems. The advantage of a Wavetrac over other helical gear setups is that it is less likekly to lose drive when a wheel becomes unloaded.

Quaife - The Quaife Automatic Torque Biasing (ATB) Helical LSD differential relies on gears rather than clutch plates for its operation. The Quaife helical LSD never locks harshly with a set pre-load of wheel slip across the driven axle. Rather, the Quaife Helical LSD automatically biases the torque away from the spinning wheel across the axle to a constantly varying degree, never locking completely.

OS Giken - The increased number of friction discs not only dramatically improves the LSD's locking force, it enables it to lock fully and completely. An added benefit to being a fully locking mechanism is that less heat is generated, thus resulting in increased durability and reliability. Special OS Giken fluid is required. OS Giken diffs are for motorsport use only and no warranty is provided.

1M Gearing Options
Gearing selection for a turbo car can be tricky. The factory specified a gear that was optimal for acceleration, smoothness, and fuel economy. All of those are affected by using a new gear ratio. On turbo cars, a shorter (numerically higher) gear ratio will get you into the boost sooner but at the expense of smoothness and traction. Some lag in a turbo system is desirable so that the car doesn't feel like an off/on switch. For street driving a stock or mildly upgraded gear is advised (3.15-3.23). Any ratio over 3.45 will be great for acceleration but will be difficult to modulate on the street. Also keep in mind the shorter gears will mean extra shifts during 1/4 and acceleration runs. The true advantage in buying a 1M differential upgrade comes from a better limited slip and getting power down. Contact our sales staff if you have any questions.

Max Speed at 7,000 RPM (click for larger)RPM at Cruising Speeds (click for larger)

Additional Options
REM Polishing - REM is a light surface polish treatment of the gears and/or bearings that removes small imperfections on the surface. This reduces internal temps and friction, improving performance and efficiency. It also makes the ring & pinion smoother and quieter. 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
There is a $1,500 core charge for your usable original diff. This charge will be in addition to the advertised price. Core exchanges help keep the overall cost low and wait times to a minimum. Therefore we require that your return your original diff to Diffsonline within 14 days. You can even re-use the shipping container and packing material. The core refund is at the discretion of the diff builder - only rebuildable cores will be accepted. You can avoid the core charge by sending in your existing diff for the rebuild.

Selecting the best differential type for your application can be a difficult task considering the amount of ratios and limited slip carriers. Please feel free to contact your BimmerWorld sales representative to discuss the best differential for your application.
BMW Fitments:--

1 Series
E82 / E88 (08-13) > 1M (11-12)
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