Decel vibration/rattle after flywheel install

[fiftytakedowns]

I have a JB racing 9lber with the stock Clutch as well.  I get a buzzing/ vibration on decel, its the same in every gear, and nearly goes away instantly once it hits 2999 RPM. Dont know if it is a Vibration in the Exhaust, or in the engine mounts going causing the motor to tilt and buzz against something on decel, but it is definitley RPM dependent.

That being said my exhaust is rattly, and has a loose baffle in the muffler which causes an annoying sound.

[dude8383]

I have a JB racing 9lber with the stock Clutch as well.  I get a buzzing/ vibration on decel, its the same in every gear, and nearly goes away instantly once it hits 2999 RPM. Dont know if it is a Vibration in the Exhaust, or in the engine mounts going causing the motor to tilt and buzz against something on decel, but it is definitley RPM dependent.

That being said my exhaust is rattly, and has a loose baffle in the muffler which causes an annoying sound.

Its your super light flywheel. Same thing happened to my friend when he bought himself an aluminum JB flywheel for his Subi. Get yourself a steel ltw M20 flywheel and the "buzzing" will go away.

[autox320]

I'd imagine installing a solid (single mass flywheel) with solid clutch (standard M42 unsprung) is a bad idea unless its a race car.
Single mass JB flywheel you'd want the non-ac version sprung hub clutch.

FWIW I have no issues with the kit we installed from Todd at dynotech. It is a cut down M20 ltw flywheel and 325i stock sprung hub clutch. Feels just as light pedal and sounds as the factory M42 setup but much more holding power. Not to mention the lighter flywheel free rev feeling as you punch through the rpms.

[nicknikolovski]

The dual mass is used for a purpose - it dampens out any vibrations and also helps with engine braking. Its crap that our M42 engine seems to have one of the heaviest ones of all the E30/E36 line-up.

[dude8383]

I'd imagine installing a solid (single mass flywheel) with solid clutch (standard M42 unsprung) is a bad idea unless its a race car.
Single mass JB flywheel you'd want the non-ac version sprung hub clutch.

FWIW I have no issues with the kit we installed from Todd at dynotech. It is a cut down M20 ltw flywheel and 325i stock sprung hub clutch. Feels just as light pedal and sounds as the factory M42 setup but much more holding power. Not to mention the lighter flywheel free rev feeling as you punch through the rpms.

Thats exactly what i'm talking about. He'd be much better of picking up m20 flywheel with a sprung 325i clutch. You can't rock an m20 flywheel with an m42 clutch anyway...215mm vs 228mm

The dual mass is used for a purpose - it dampens out any vibrations and also helps with engine braking. Its crap that our M42 engine seems to have one of the heaviest ones of all the E30/E36 line-up.

Yep, and thats precisely why picking up a full m20 flywheel/clutch kit is worth it. Just have a machine shop lighten the flywheel a bit to gain some more peppiness!

[bmwman91]

Holy thread resurrection, Batman!

I was doing a web search for "E30 input shaft rattle" and this was one of the hits. Recently I installed a Metric Mechanic engine with an 11lb (lightened) M20 flywheel. I get really loud rattling when sitting at idle with the clutch pedal up. The noise was there in the past with a stock 19lb M20 flywheel, but not as loud, and I assume that this louder version of the same noise is a result of the lighter one.

The new thing is, as some have mentioned above, rumbling/rattling when I let off the gas and engine-brake. I am using a full M20 clutch with a sprung-disc, so it isn't a solid setup. From what I have read here, it sounds like the noise is really just an annoyance, and that it poses no real threat? I also installed some AKG Delrin shift arm bushings (the ones that the "bitch clip" goes through) and I have to assume that some noise is being transmitted up through the shifter that way too.

Thoughts? If it is just a normal noise, I am fine with it. Is there any risk to tranny reliability here? Thanks!