Updated advice on machining Dual Mass Flywheel?
04-14-2016, 06:35 AM
#1
Burning Brakes
Thread Starter
Updated advice on machining Dual Mass Flywheel?
I've read a few threads on this but some are 5-7 years old and some ppl have said yes, others no. I also read mixed things about going Single Mass but will stay w/ DM bc this C4 could become my daily driver.
The Corvette Shop in Canoga Park, CA (socal) said they'd machine mine for $70 if they didn't think it needed to be replaced. I don't know that shop though and no one's said much about it in a thread I have for it in the socal section.
I've seen this gentleman pop up 3 times in threads for machining: http://www.powertorquesystems.com/Contact.htm
BUT I'm guessing this is for those doing to do their own clutch replacement (I cannot) I'm assuming no shop will want liability for a part they didn't machine.
To machine or not to machine? I'd appreciate some updated advice
btw I haven't forgot the advice from a couple of you to check out the slave & master before going for a full clutch & flywheel work. I'm gathering info/advice
The Corvette Shop in Canoga Park, CA (socal) said they'd machine mine for $70 if they didn't think it needed to be replaced. I don't know that shop though and no one's said much about it in a thread I have for it in the socal section.
I've seen this gentleman pop up 3 times in threads for machining: http://www.powertorquesystems.com/Contact.htm
BUT I'm guessing this is for those doing to do their own clutch replacement (I cannot) I'm assuming no shop will want liability for a part they didn't machine.
To machine or not to machine? I'd appreciate some updated advice
btw I haven't forgot the advice from a couple of you to check out the slave & master before going for a full clutch & flywheel work. I'm gathering info/advice
Last edited by jay23ls; 04-14-2016 at 06:39 AM.
04-14-2016, 07:11 AM
#3
You're somewhat handicapped by just having a shop doing the clutch install. If this were a DIY time might not be such a detrimental issue. A shop needs the "stall space" the stall/lift is money.
So much depends on the condition of it when removed, actually everything depends on it. Was this an original clutch or was this maybe a replacement and has already seen some "tinkering". You've no way to tell. Condition and measuring the thickness of what's removed is key. Until it's in your hands you don't know that it's the dual-mass, assume yes but a matter of fact no.
I'd want to have a discussion with the machine shop and ask the procedure they use to surface/refinish the dual-mass. Bring that discussion back here maybe.
Dual-mass have been resurfaced/refinished for years. Procedure important.
So much depends on the condition of it when removed, actually everything depends on it. Was this an original clutch or was this maybe a replacement and has already seen some "tinkering". You've no way to tell. Condition and measuring the thickness of what's removed is key. Until it's in your hands you don't know that it's the dual-mass, assume yes but a matter of fact no.
I'd want to have a discussion with the machine shop and ask the procedure they use to surface/refinish the dual-mass. Bring that discussion back here maybe.
Dual-mass have been resurfaced/refinished for years. Procedure important.
Last edited by WVZR-1; 04-14-2016 at 07:15 AM.
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jay23ls (04-14-2016)
04-14-2016, 07:14 AM
#4
Race Director
I guess I would question the machinist or machine shop about a minimum thickness specification. I don't actually know if there is one for your flywheel but its possible to cut a flywheel to thin which will cause clutch disengagement problems.
04-14-2016, 07:42 AM
#5
Melting Slicks
When I was doing the clutch replacement on my 94' back in 2012 and speaking with Bill B. and Jim Jandik, they both recommended I just clean the surface of the dual mass flywheel with a maroon scotch brite pad. I did exactly that, and have been fine for 20+ thousand miles. The car had approximately 105k miles on it at the time of the clutch R&R.
04-14-2016, 07:50 AM
#6
When I was doing the clutch replacement on my 94' back in 2012 and speaking with Bill B. and Jim Jandik, they both recommended I just clean the surface of the dual mass flywheel with a maroon scotch brite pad. I did exactly that, and have been fine for 20+ thousand miles. The car had approximately 105k miles on it at the time of the clutch R&R.
TT94 - Do you?
04-14-2016, 08:05 AM
#7
Melting Slicks
https://www.corvetteforum.com/forums...questions.html
DMF before Scotchbrite:
DMF after Scotchbrite:
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jay23ls (04-14-2016)
04-14-2016, 08:13 AM
#8
^^^^^
That should be a good read for the OP and your last comment regarding your ZF in the "other thread" is that your '94 isn't ODD at all. I would expect nothing but a "black tag" in a '94. That's so long as it were original. That's why I mentioned to the OP in his other thread to check the number and tag color on his before starting.
That should be a good read for the OP and your last comment regarding your ZF in the "other thread" is that your '94 isn't ODD at all. I would expect nothing but a "black tag" in a '94. That's so long as it were original. That's why I mentioned to the OP in his other thread to check the number and tag color on his before starting.
04-14-2016, 08:19 AM
#9
Melting Slicks
^^^^^
That should be a good read for the OP and your last comment regarding your ZF in the "other thread" is that your '94 isn't ODD at all. I would expect nothing but a "black tag" in a '94. That's so long as it were original. That's why I mentioned to the OP in his other thread to check the number and tag color on his before starting.
That should be a good read for the OP and your last comment regarding your ZF in the "other thread" is that your '94 isn't ODD at all. I would expect nothing but a "black tag" in a '94. That's so long as it were original. That's why I mentioned to the OP in his other thread to check the number and tag color on his before starting.
04-14-2016, 04:10 PM
#10
Burning Brakes
Thread Starter
The OP's flywheel is going to be pretty bad, regardless of "tinkering", mileage, or anything else. Because it has been SLIPPING BADLY. He mentions in his other thread "it will hardly get up to speed in 1st and 2nd" and "smell of clutch". It's so bad, he's towing it for repairs because it can't be driven. It's slipping. The flywheel is being subject to tremendous heat. This will result in the formation of blue spots and uneven hardness on the surface. This unevenness makes it very difficult to machine without tool chatter.
A dual-mass flywheel contains springs within the assembly. The heat deteriorates and damages the springs. Machining isn't going to restore the mechanism within the flywheel. There is a specification for how much play can be present between the inner and outer elements. IIRC, it's about 3/8 of an inch. Continuing to drive it once slipping is detected is detrimental to the flywheel. Especially a Dual Mass. The 92 that I did wasn't slipping, it had other problems that required it to come out. The flywheel had some spots but cleaned up nicely with scotchbrite. My experience tells me the OP's flywheel is going to be junk. It has suffered a LOT of heat in the last few miles of its life.
As a complete side comment: I thouroughly enjoyed driving the 92 with its 6-speed after I completed the clutch work. Completely different feel than my 4+3, the ratios, the shift action, etc. But if I were to contemplate purchasing a car with a 6-speed I'd be very cautious regarding the clutch. These flywheels are a Pandora's box of potential grief. Particularly now that new ones are no longer available. Replacements with zero-balanced units can cause engine vibration. It's a swamp. Personally, I'd be more inclined to purchase an automatic. Avoid this DM flywheel thing all together. There is no good, easy, or inexpensive way out. I can rebuild a 4L60e for about $350 in parts. This guy is looking at $2,500 for his clutch repairs. And the car may have engine harmonic vibrations after the work. I wish him luck.
A dual-mass flywheel contains springs within the assembly. The heat deteriorates and damages the springs. Machining isn't going to restore the mechanism within the flywheel. There is a specification for how much play can be present between the inner and outer elements. IIRC, it's about 3/8 of an inch. Continuing to drive it once slipping is detected is detrimental to the flywheel. Especially a Dual Mass. The 92 that I did wasn't slipping, it had other problems that required it to come out. The flywheel had some spots but cleaned up nicely with scotchbrite. My experience tells me the OP's flywheel is going to be junk. It has suffered a LOT of heat in the last few miles of its life.
As a complete side comment: I thouroughly enjoyed driving the 92 with its 6-speed after I completed the clutch work. Completely different feel than my 4+3, the ratios, the shift action, etc. But if I were to contemplate purchasing a car with a 6-speed I'd be very cautious regarding the clutch. These flywheels are a Pandora's box of potential grief. Particularly now that new ones are no longer available. Replacements with zero-balanced units can cause engine vibration. It's a swamp. Personally, I'd be more inclined to purchase an automatic. Avoid this DM flywheel thing all together. There is no good, easy, or inexpensive way out. I can rebuild a 4L60e for about $350 in parts. This guy is looking at $2,500 for his clutch repairs. And the car may have engine harmonic vibrations after the work. I wish him luck.
I would have got it towed the last 1-2 miles if I would have known how the clutch works better and how
1. SMF is not always a good sub
2. DMF is hard/impossible to find
3. DMF is 1,000 bucks
It could have saved the flywheel
In my search for clutch repair cost before I looked at the car, I only found regular costs not involving the DMF of about $1,500 so I didnt dive into the DMF research then.The shop says they'll do an OEM DMF replacement. Don't know where they'd find one but I'm going to go in-person to talk to them before I get the car towed there.
Looks like I'll end up paying a bit of premium for not wanting to wait about a year for a local 6 speed Admiral Blue C4 w/ great paint. I just gotta take care of things and get the car to run great now.
Last edited by jay23ls; 04-14-2016 at 04:21 PM.
04-14-2016, 04:19 PM
#11
Burning Brakes
Thread Starter
About the engine harmonic vibrations, These are less likely to happen if replacing w/ a DMF instead of SMF correct? Something about the balancing being harder/trickier on a SMF I think?
Last edited by jay23ls; 04-14-2016 at 04:22 PM.
04-14-2016, 04:24 PM
#12
Race Director
Don't give up on the flywheel you have until you see it. The guy who posted the pic of his flywheel must have gotten it pretty hot at some point. There blue all over it.
04-14-2016, 04:30 PM
#13
Burning Brakes
Thread Starter
I'm assuming that's what the shop will do or at least should do
This might be a dumb question but is the C4s DMF accessible like in the video?
Last edited by jay23ls; 04-14-2016 at 05:01 PM.
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DaveP85C4 (04-21-2016)
04-14-2016, 05:09 PM
#14
Race Director
Yeah, its worth at least a look and the test on the movement/give for the springs or spring action. I found this on testing:
https://www.youtube.com/watch?v=joe3x_e6ug4
I'm assuming that's what the shop will do or at least should do
This might be a dumb question but is the C4s DMF accessible like in the video?
https://www.youtube.com/watch?v=joe3x_e6ug4
I'm assuming that's what the shop will do or at least should do
This might be a dumb question but is the C4s DMF accessible like in the video?
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jay23ls (04-14-2016)
04-14-2016, 05:17 PM
#15
Burning Brakes
Thread Starter
Its accessible after the transmission is out of the way. I wouldn't get your hopes up as far as someone doing any testing like in the video. I'm guessing there will be a close visual inspection and a lot of hope. Its unlikely there will be any testing. That's my guess. If there's any suspicion about the parts after visual inspection they should certainly tell you and let you decide how you want things handled.
A poorly/improperly machined DMF won't cause anything catastrophic right like a ruined trans or engine..? Bc if there's any chance, I'll just shell out the $ for a new one. The shop says they can get one. I'll need to see proof of that man.
04-14-2016, 05:33 PM
#16
Race Director
Ok thanks for the accessibility info. I'll talk to the shop to see what they do if they machine it and it causes issues later.
A poorly/improperly machined DMF won't cause anything catastrophic right like a ruined trans or engine..? Bc if there's any chance, I'll just shell out the $ for a new one. The shop says they can get one. I'll need to see proof of that man.
A poorly/improperly machined DMF won't cause anything catastrophic right like a ruined trans or engine..? Bc if there's any chance, I'll just shell out the $ for a new one. The shop says they can get one. I'll need to see proof of that man.
04-14-2016, 05:38 PM
#17
Burning Brakes
Thread Starter
Personally I bet the mechanic never even pulls the flywheel off the crank. He will scotch brite the thing with his die grinder and slap it together. If you can get the correct flywheel new then there's certainly nothing wrong with replacing it. If they tell you to replace it and you wont then they wont warranty anything. I'm not sure if availability is the issue with these flywheels or if its the expense. I'm sure someone else knows.