Play in DM???
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Joined: Mar 2005
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From: Walton KY
Play in DM???
94 coupe 6 speed 105K miles.
How much play should be in a DM flywheel? Manual says 35MM (1.378 inches) but how much pressure should it take to do that? Is it possible to have broken the DM and not know it?
Reason I ask. At the strip clutch would slip in 3rd and 4th...pedal it and the clutch would grab but too late. Got it all apart and the disc looks pretty good and the fly wheel doesn't have any bluing at all, just some (25?) small 1/8th inch round black spots. Flywheel came off a new LT4 crate motor and installed on my car about 5000 miles ago. Motor is out adding cam, 1.6 roller rockers, lifters, push rods, oil pan & pump, clutch, and long tubes along with some maintence items like new power steering lines & rack, steering column, brake master cylinder.
How much play should be in a DM flywheel? Manual says 35MM (1.378 inches) but how much pressure should it take to do that? Is it possible to have broken the DM and not know it?
Reason I ask. At the strip clutch would slip in 3rd and 4th...pedal it and the clutch would grab but too late. Got it all apart and the disc looks pretty good and the fly wheel doesn't have any bluing at all, just some (25?) small 1/8th inch round black spots. Flywheel came off a new LT4 crate motor and installed on my car about 5000 miles ago. Motor is out adding cam, 1.6 roller rockers, lifters, push rods, oil pan & pump, clutch, and long tubes along with some maintence items like new power steering lines & rack, steering column, brake master cylinder.
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Pro
Joined: Mar 2005
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From: Walton KY
I did replace it. It only has 5000 miles on AC clutch kit and new LT4 DM. Not even sure it has that many miles on it. The car is 85% street driven. How much chatter and/or notice can expect from a single mass steel?
Last edited by dchildress; Sep 8, 2014 at 03:45 PM.
Team Owner
Joined: Aug 2000
Posts: 40,156
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From: San Pedro CA
chatter, none.
If you match balance it, the clutch will behave just like OEM, and be lighter and more responsive.
The old recipe was to use an Fbody flywheel, cut down .090, then balanced, use a Corvette pressure plate and conventional sprung hub disc.
To match balance, the two flywheels are put on a common axis, 180* out of phase. As they spin up, the machine indicates where to put the added weight.
Here is the score on the OEM clutch... it's serviceable... sure, but for racing? meh... not so much. It is organic and once glazed, becomes rather useless.
Using even a stock engine, I would want a stage II clutch for racing. It will have more bite, but will also be streetable. A stage III would be intolerable on the street... think on/off switch.
The DM is the same for all LTx and L98's. the pressure plates are different on the LT5.
If you match balance it, the clutch will behave just like OEM, and be lighter and more responsive.
The old recipe was to use an Fbody flywheel, cut down .090, then balanced, use a Corvette pressure plate and conventional sprung hub disc.
To match balance, the two flywheels are put on a common axis, 180* out of phase. As they spin up, the machine indicates where to put the added weight.
Here is the score on the OEM clutch... it's serviceable... sure, but for racing? meh... not so much. It is organic and once glazed, becomes rather useless.
Using even a stock engine, I would want a stage II clutch for racing. It will have more bite, but will also be streetable. A stage III would be intolerable on the street... think on/off switch.
The DM is the same for all LTx and L98's. the pressure plates are different on the LT5.
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Pro
Joined: Mar 2005
Posts: 666
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From: Walton KY
I already have the clutch. I bought a Centerforce. I don't think I want an aluminum FW. How do I know for sure if I have cooked the DM? I can't imagine that 40 passes would have cooked a brand new DM. Any brand of steel one piece you recommend?
Last edited by dchildress; Sep 9, 2014 at 01:05 PM.
Le Mans Master
Joined: May 2005
Posts: 7,355
Likes: 2,280
From: Central Maryland
Bogus's advice about the Spec Stage 2 clutch is good, for a street-driven car that sees some aggressive use. I installed a Spec Stage 2 clutch kit, along with one of the Spec extra-weight billet steel single-mass flywheels three years ago in my '94. I'm very pleased with it. The clutch action is slightly grabby with a mild amount of chatter when it's stone cold. After a couple of engagements, it's silky smooth.
The extra-weight SMF seems to have kept gear rattle down to an absolute minimum in my car. I can barely hear it when the ragtop and windows are up (which is rarely the case). I seriously doubt anybody else would ever hear it, and nobody has ever commented on it. Gear rattle with SMFs seems to vary a lot from car to car, and is especially influenced by the weight of the SMF. More mass helps to reduce rattle, but doesn't guarantee you won't have any.
Live well,
SJW
