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DISCUSSION => Engine + Driveline => Topic started by: D. Clay on March 11, 2007, 05:10:57 PM

Title: Dual mass flywheel.
Post by: D. Clay on March 11, 2007, 05:10:57 PM

Do the dual mass flywheels ever go bad and require replacement? Anyone know how they work?

Title: Dual mass flywheel.
Post by: badboypolar on March 11, 2007, 09:14:56 PM

Yes they go bad and will need replacement.

Well the have two (dual) masses and are connected by a series of bolts and springs. When the flywheel is subject to vibration or too much torque the springs inside take the brunt of it. There is a better explanition and I will try to find it.

Title: Dual mass flywheel.
Post by: bmwman91 on March 11, 2007, 10:46:13 PM

Yeah, they can wear out eventually.  Any sort of catastrophic failure is highly unlikely, but annoying chatters and whatnot can become apparent.

The springs can break (uncommon), and be subject to losing some stiffnes.  Other internal components can be subject to deformation/bearing failures over time leading to this.  So yeah, they can wear out so to speak, but the car should still be driveable.  Shifting might be rough and clunky, but that's about it.  That's about the extent of my dual-mass flywheel knowledge.

Title: Dual mass flywheel.
Post by: b318isp on March 12, 2007, 04:02:19 AM

My wife's Alhmabra's flywheel gave trouble (internally collapsed covering the bellhousing and clutch in grease). Fortunately, DM flywheel trouble GENERALLY seems limited to diesels as they are prone to much higher levels of peak torque - I've yet to hear of one going on a petrol BMW. The DMF is actually used in modern diesels to stop the engine shattering/sheering gearbox teeth!

Title: Dual mass flywheel.
Post by: D. Clay on March 12, 2007, 10:08:01 AM

I have a slight clunk at low speeds when you let off the gas quickly. It's like the rear end has too much backlash but it comes from the trans/clutch  area. Nothing appears wrong with the transmission except a little whining sound in second at steady speed. Nothing abnormally loud for an old transmission and it shifts as good as ever. I thought maybe the flywheel springs could be weak a letting it hit whatever stops are there internally.

Title: Dual mass flywheel.
Post by: b318isp on March 12, 2007, 10:22:09 AM

Sounds normal to me. Check the guibo though and make sure the centre prop shaft bearing's rubber surround it is intact.

Title: Dual mass flywheel.
Post by: D. Clay on March 12, 2007, 11:31:59 AM

Have just replaced guibo, rear trans seal and CSB. I think it may the evidence of 200,000 miles.