Drivetrain Questions and info regarding transmissions, clutches, etc.

DMF failure symptoms?

  #1  
Old 01-09-2019, 03:10 PM
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DMF failure symptoms?

Anyone on here experienced a failed dual mass flywheel on a 6MT, or replaced a worn one before total failure? If so what were your symptoms and what improved when you got a new one?

Ever since I got my poly engine/trans mounts I noticed some vibration around 2000 RPM while revving in park and while driving. This was even after the mounts broke in and the idle smoothed out. At that point I just chalked it up to the poly mounts.

Recently, it's been getting worse, and engine vibrations are starting to intensify lower in the RPM range ~1400 RPM, at idle, and now around 2500 RPMs I sometimes get a much stronger vibration that I can make go away if I smash the gas pedal on and off and shock the system back into balance. At the same time this has been happening, my shifter has been feeling a bit "looser" during shifting and the feeling of having drive train slop when releasing the clutch has also increased, despite poly everywhere but the subframe.

I've had my drivetrain inspected and the only thing externally wrong is I had way too much play in my diff output bearings, which I already knew because of the whining my car has always had. There's also a TINY amount of play in the transmission tailshaft bushing up and down, if anyone has that part number I'd really appreciate the link.

Now when turning the car off, I hear rattling coming from the engine bay. There's no clunking or other noises while driving or starting out.

The original owner put in a stage 2 clutch and new master and slave cylinders 70k miles ago, but did not mention replacing the flywheel. Since then, it's been to the track at least a dozen times and gets run up to 90+ mph almost daily.

Thoughts? I was hoping by buying a car with an aftermarket performance clutch I wouldn't have to pull the tranny on my daily but unfortunately that may have been wishful thinking.


 
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Old 01-09-2019, 03:23 PM
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It will feel fine for the first few miles, then you will notice a lot more feel of drivetrain play when you let on/off the throttle. What happens that causes DMFW to fail is the springs that hold the center balancing plate wear out and the plate starts to slam from one end to the other when you go on and off the throttle and it feels VERY jarring when it happens, you will think it's coming maybe from the rear differential and something is loose but it's probably the flywheel.

When those springs are cold they stiffen slightly so it will feel sorta normal for a few miles, then they get heat soaked and get really loose and sloppy and it starts to.feel really bad.
 
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Old 01-09-2019, 10:19 PM
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That is EXACTLY what happens. Jerking the engine helps the vibes by moving around the remains of broken springs to balance the assembly better.

Do you have any experience with heavier weight single mass steel flywheels and chatter? I don't want a horrible cement mixer noise like with the JWT flywheels but at the same time won't pay $400 for another DMF. I'm either going to find a used brand name steel flywheel or get one on amazon as part of a clutch kit (that I'll sell for $50) and have a machine shop give it a once over.
 
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Old 01-10-2019, 12:54 PM
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I'm using the 14# Z1 motorsports flywheel, it's got a little chatter but honestly you should try to find someone locally with a lightweight one so you can hear it in person, it's not nearly as bad as you're describing.

I know LUK makes a quality replacement DMFW for probably the cheapest price you will find, it's usually around $450 and you won't have ANY chatter and a complete OEM feel while driving.
 
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Old 01-10-2019, 03:07 PM
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Well for 150 bucks I can get an (China) XTD 19 lb steel single mass flywheel, add another 75 bucks to balance everything and I should be back in business.

If my clutch is cooked or crappy looking im going to give the z1 mild performance clutch with sprung full face disc a try. Might reuse my old pressure plate for more clamp force, but not sure yet. I know my pedal is at least 2x harder than stock.

Time to baby the G on my daily hour long highway commute for the next 3 months until I have the space to drop the tyranny.
 
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Old 01-10-2019, 04:00 PM
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I will say this, when my original OEM DMFW shat the bed it was a LOT louder and more chatty than my lightweight single mass one is right now. Mine started making this terrifying "clackety" sound when I would take off from a stop.
 
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Old 01-10-2019, 04:33 PM
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Great, so by the time I take this one off the lightweight one will seem luxurious in comparison. Thanks again for the advice.
 
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