ACT 09-13 BMW 135i / 09-13 335i XACT Flywheel ProMass

ACT 601030 is a single-mass chromoly flywheel for the turbocharged 3.0-liter BMW six with a manual gearbox, listed here for the 2009-2013 135i and 335i. It is the part people search for when the factory dual-mass flywheel starts to rattle, shudder or slip, and it is also the flywheel ACT pairs with its BM14 clutch kits, which cannot run on the stock flywheel. Note on naming: our listing title says ProMass, but ACT catalogs part number 601030 as an XACT Streetlite flywheel, and the part number is what you receive.

What this flywheel does on an N54 or N55 BMW

From the factory these cars use a dual-mass flywheel, two plates joined by springs that soak up firing pulses so the gearbox stays quiet. Those springs wear out, especially behind a tuned engine. 601030 replaces the assembly with one forged, CNC-machined piece. ACT lists it at 17.9 pounds with a 9.4-inch (240 mm) friction surface, a 115-tooth induction-hardened ring gear and SFI 1.1 certification. Removing the dual-mass spring pack sharpens throttle response and gives the clutch a solid, flat surface that will not warp or loosen, and ACT notes the surface can be resurfaced later without extra parts. Our dual-mass vs. single-mass comparison explains the trade-offs in detail.

The cost of that conversion is noise. ACT states gear rattle is expected, typically OE to mild, most noticeable at idle in neutral.

Symptoms of a failing factory dual-mass flywheel

• Knocking or rattling at idle that goes away when the clutch pedal is pressed
• Shudder or vibration when pulling away, especially in first and reverse
• A clunk on engine shutdown or when getting on and off the throttle
• Clutch slip at higher boost that a new disc alone does not fix

Our dual-mass flywheel failure guide goes deeper on each symptom and what a replacement costs.

How to confirm before you buy

With the engine idling in neutral, listen for rattle from the bellhousing, then press the clutch; if the noise drops away, the flywheel damper is the likely source. Once the gearbox is out, check how far the two halves of the flywheel rotate against each other and look for grease leaking from the spring cavity. If the real complaint is slip, run the test in our slipping diagnosis guide and read shift flare vs. slip to be sure the issue is in the clutch.

Fitment

We list 601030 for the 2009-2013 BMW 135i and 335i manual. ACT's own chart also covers the 335is, 335xi and xDrive models, F30 335i to 2015, 435i to 2016, 535i and the Z4 sDrive35i, all with the 3.0-liter turbo six. ACT specifies it for the 6-bolt crankshaft. Some earlier N54 cars use an 8-bolt crank flange that needs a different flywheel, and catalogs do not all agree on exactly which build dates changed, so count the flywheel bolts on your crank before ordering, or send us your year and VIN and we will confirm it. Other drivetrain parts are in our hard parts section.

Install notes

• 601030 works with the factory clutch or an ACT kit; ACT's BM14 kits require an ACT flywheel, such as the BM14-HDSS street kit.
• Use the supplied M12-1.5 x 25 mm flywheel bolts, never the old stretch bolts, and torque them evenly in a cross pattern.
• Replace the pilot bearing and release bearing while you are in there, and lightly grease the input splines.
• Bleed the clutch hydraulics after reassembly and break the clutch in gently; see our clutch break-in guide.

For a tuned car making well past stock torque, the BM14-XTSS Xtreme street kit is the natural partner for this flywheel.

Is 601030 a ProMass or a Streetlite flywheel?

Our listing title says ProMass, but ACT's current catalog lists part number 601030 as the XACT Streetlite flywheel: forged chromoly, 17.9 lb, 240 mm friction surface, 115-tooth ring gear. The part number is the item you receive.

Can I use it with my stock BMW clutch?

Yes. ACT states 601030 can be used with both the factory clutch kit and ACT clutch kits. ACT's BM14 kits must be used with an ACT flywheel.

Will it fit my 2008 335i?

ACT's chart for 601030 starts at 2009 and specifies the 6-bolt crankshaft. Some earlier N54 cars have an 8-bolt crank and need a different flywheel. Count the crank bolts or send us your VIN and we will check.

Will my car be louder with a single-mass flywheel?

Yes. ACT says gear rattle is expected with this single-mass conversion, generally OE to mild, mostly at idle in neutral.

Are flywheel bolts included?

Yes, ACT includes M12-1.5 x 25 mm flywheel bolts. Do not reuse the factory bolts.

• How to Diagnose Transmission Slipping
• Shift Flare vs. Slip: How to Tell Them Apart
• Automatic vs. Manual Transmission Repair Cost