3.9 g6 GXP flywheel

[NateD4]

Has anyone had any trouble with the dual mass G6 F40 GXP 6 speed manual flywheel?

I'm looking at using one in a boosted application.

[Google Adsense]

[robertisaar]

Joseph Upson would be a good person to ask about this, but i believe he had his stock setup sent out to someone to have it's torque capacity tested and the results were that it could only hold up to ~10% over stock levels?

[pocket-rocket]

I've seen plenty of videos from things like VWs and Caddies dual masses going bad. Didn't Joseph bolt his together to make it one solid unit?

[Joseph Upson]

My flywheel is a modified 3.4L rwd flywheel to accept the smaller diameter ring gear. The 10% estimated increase limit margin was directly from a SACHS representative.

Here is a link to a one piece aluminum replacement that will set you back about $700

http://imageshack.us/g/17/clutchflywheel1.jpg/

[NateD4]

What did the Sachs rep tell you about the flywheels?

I'm not sure I need a replacement flywheel for the stock unless someone has record of breaking one. The stock flywheel has shock and vibration tuning 'stuff' in it.

I am planning more HP but inertia isn't a concern at present. Any other info would be great.

Thats an expensive flywheel. I've gotten quotes in the $500 range.

[robertisaar]

you won't "break" the flywheel, however, if you look up how dual-mass flywheels work, you'll see that there are springs inside the flywheel that allow the two portions of the flywheel to move independantly of each other, but once the springs start getting close to the maximum limit of their compression, there is a friction ring that will start slipping to prevent the springs from just outright failing. now, if the friction ring starts having to slip too often(under higher TQ loads than the 240 + ~10% quoted), it WILL burn out and you'll be left with a flywheel that's completely useless as it will just slip against itself all the time.

if you're a member of any diesel forum that caters to any of the cars/trucks that came equipped with a DM flywheel, you'll quickly see how much they hate them as well.

i'm not sure how feasible it is, but you MAY be able to permanantely lock the two halves together, giving you a heavy flywheel that would stand up to plenty of abuse.

[NateD4]

I didn't know there was a clutch internal to the flywheel. I thought it was rubber or urethane. The springs make sense.

maybe I should take it a part and see what makes it tick. I can probably have an aluminum one made fairly easily. My concern was that they have harmonics that will damage my trans. So I'd hate to lose the damping. Perhaps I can beef up the friction material.

[robertisaar]

http://www.youtube.com/watch?v=YnaXB8q3uzQ

that was a wonderful video for me, as i didn't exactly understand how they worked until i saw it. it doesn't show the friction ring being exceeded(or shown at all now that i think of it), but it would give you a good idea.

[Joseph Upson]

The G6 flywheel has grease in it along with any springs. The dual mass configuration for cars probably has more to do with reducing transmission noise especially due to the 6th gear than it does transmission protection. When it's replaced with a solid piece the transmission produces more chatter at idle. The corvettes do the same when a solid piece is installed.

The HO 3.9 G6 had about 10% more power at 270, but the torque increase was less at around 258 lb/ft suggesting GM was aware of the dualmass flywheel limits.

I experienced a small slip with my first motor but am not sure if it was the flywheel or the clutch though I suspect the flywheel because the stock G6 pressure plate applies enough pressure (2000 lbs) to hold well above the flywheel's expected limit.

[NateD4]

I didn't know GM made a 270 HP HO version of the 3.9. Any idea what was different?

I'm messing with an LZG with 6 speed.

As for the flywheel. Who made yours?

I have heard there is a company that will make one from 4340.

I also have an aluminum blank I can make one from. However, I think for now I will use the stock flywheel. I may pop the rivets off after what you have told me and rebuild it with ceramic friction material. Have you had one apart before?