Loose Flywheel, Crankshaft done for?

aireoh · 01-06-2018, 02:33 AM

Alright guys, i need some advice.
Before i start off, i'll list the mods that could be causing the following problems:
JWT CAMS
SPEC TWIN DISC CLUTCH & LIGHTWEIGHT FLYWHEEL
STILLEN LIGHTWEIGHT UD PULLEY

April 15th, 2017
So about a half a year ago, my flywheel came loose. Only reason i figured it was that was because it was chattering way beyond normal flywheel chatter.
So i removed it, i had to pry it off 'cause it was literally melted onto the back of the crankshaft. I ran into a problem when i removed it... One of the flywheel bolts had snapped inside one of the crankshaft bolts. I tried everything in my power at the time to remove the broken stud, but i couldn't. So i reinstalled my new clutch and flywheel with just 7 out of the 8 flywheel bolts.

September 6th, 2017
The car ran perfectly fine, put over 10k miles on it. I was driving from CA to AZ, when another Z caught up to me in the middle of the dessert, and he started slowing down next to me so i gave him a 40mph in 2nd gear. As soon as i shifted into 3 gear and left off the clutch, i heard a huge explosion. Whatever happened underneath claimed my transmission, transmission input shaft, slave cylinder, pressure plate, clutch, headers, A/F sensors, test pipes, steering column and starter connector. What was untouched was the flywheel, it was still attached to the crank with all of the original 7 of the 8 bolts.

Nevertheless, i removed everything cleaned what i could, bought new parts... I ended up spending a little under $5,000. I reinstalled the clutch and flywheel with only 7 of the 8 bolts again 'cause the old flywheel was solidly attached when i removed it. It must've been something behind the flywheel that malfunctioned and just detonated inside my tranny bell housing.

November 1st, 2017
I'm driving in Cali i feel the clutch pedal abnormal vibrating with every shift, and just cruising. I take a wild guess and say it's something drivetrain related.
So i drive back home to Arizona, knowing i'm taking a huge risk.
I remove the transmission when i get home and what do i find? Everything is fine BUT the new flywheel. i remove the pressure plate just to find that 2 more bolts are snapped inside the crankshaft to make it a total of 3 studs stuck in the crankshaft.
Circled in red is the original stud i tried removing from back in April.

At this point i've had enough, i bought some gold tipped drill bits and do what i can to remove the studs. Long story short, i removed all of the studs that were stuck in the crank.

Here's the crank with all of the studs removed.

Reinstalled Flywheel and clutch with all of the 8 bolts. I cleaned and retapped every bolt hole just to make sure the bolts would fit perfectly. I sanded the back of the crank down to where everything was smooth and the flywheel would sit flush. Torqued & Locktite was applied.

January 1st, 2017
I feel the same vibration i felt two months ago. I say to myself, okay it's gotta be the flywheel again. I ignore it to see if it would go away... I was wrong, the chattering got really bad, like back in April to the first occurrence.
So i drove back to AZ on January 3rd, 2017.
I just finished pulling the transmission yesterday, and just like i suspected... The flywheel was hanging on by literally a thread.. how did i make it back? I have no clue, but it was stupid driving it such a long distance, i know. I literally shook the flywheel twice and it came off, pressure plate, clutch and all. And come to find that there are now 4 broken studs in the crank.

I'm at the point where i don't know what the best option would be.
1.) Pull motor, replace crankshaft. 2.5k. (Since this motor has JWT cams)
2.) Buy a used motor and have it fully replaced for 2k.
3.) Buy a brand new motor and have it fully replaced for 3k.
4.) Drill out studs, buy ARP bolts and locking washers and reinstall the same clutch kit.

The Z as she sits now.

Please send help.

Chuck33079 · 01-06-2018, 07:14 AM

Whatever you do, get rid of the Spec garbage. I don't know if it caused all that destruction, but it sure didn't help.

SouthArk370Z · 01-06-2018, 07:56 AM

You made several unsuccessful repairs. Either:
A) You don't have the resources to do the repair properly or
B) The crank is beyond repair

If it's A, then a good machinist will be able to fix it
If it's B, then a good machinist will be able to tell you.
Find a good machinist and get their opinion. I'm betting that the crank is trashed.

Your option 4 sounds like the worst possible thing to do - you haven't fixed the root problem.

aireoh · 01-06-2018, 03:23 PM

Quote:

Originally Posted by Chuck33079

Whatever you do, get rid of the Spec garbage. I don't know if it caused all that destruction, but it sure didn't help.

i’ll take that into consideration, i thought it was a good clutch kit.

aireoh · 01-06-2018, 03:30 PM

Quote:

Originally Posted by SouthArk370Z

You made several unsuccessful repairs. Either:
A) You don't have the resources to do the repair properly or
B) The crank is beyond repair

If it's A, then a good machinist will be able to fix it
If it's B, then a good machinist will be able to tell you.
Find a good machinist and get their opinion. I'm betting that the crank is trashed.

Your option 4 sounds like the worst possible thing to do - you haven't fixed the root problem.

well i don’t think you can repair the crank better than what i did while it’s installed in the engine.
i’m still searching around for options, but going back to the swapping out the motor + new clutch and flywheel sounds best.

SouthArk370Z · 01-06-2018, 04:58 PM

Quote:

Originally Posted by aireoh

well i don’t think you can repair the crank better than what i did while it’s installed in the engine.

And, realistically, you probably can't do better with the crank out. Take it to someone who can determine if the crank (and the clutch/flywheel) can be fixed. Going by the pics, my guess is that the crank is scrap metal. And I wouldn't be surprised if the clutch/flywheel hasn't been damaged beyond repair.

Quote:

Originally Posted by aireoh

i’m still searching around for options, but going back to the swapping out the motor + new clutch and flywheel sounds best.

Get a professional opinion on the condition of the crank (and clutch/flywheel) before replacing everything (they may be able to tell from the pics). A real machinist might be able to fix it.

SG4247 · 01-07-2018, 05:42 AM

Hard to tell much from the pics, but here is what I would do:

1. Pull the spark plugs.
2. Use a stone and buff off the burrs on flange until it is flat. Put a dial indicator on the rear crank flange face and turn the crank by hand to determine if there is axial run-out on the flange (bent flange from the previous boom). It should be nearly zero. Maybe .001" - check the service manual for the spec.
3. With the same indicator, check the crank thrust end play with a pry bar. The clutch may have damaged the thrust surface on the crank. End play should be .005" - .008" guessing - check the service manual for the spec.
4. Turn the crank by hand, does it feel unusually tight in spots?
5. Drain the engine oil and check for main bearing material in the oil.
6. Inspect the flywheel bolt hole threads for cracks and hole elongation with a long bolt (3"-4" long) of the proper thread size and pitch. A good bolt hole will have a good fit and the long bolt wont wobble much when fully engaged in the treads. You can easily tell a good bolt hole from a bad one using a 3-4" long bolt as a gauge.

If all that checks good, put in a new clutch/flywheel that is precision balanced, using ARP hardware.

SG4247

Trips · 01-07-2018, 11:20 AM

Quote:

Originally Posted by SG4247

Hard to tell much from the pics, but here is what I would do:

1. Pull the spark plugs.
2. Use a stone and buff off the burrs on flange until it is flat. Put a dial indicator on the rear crank flange face and turn the crank by hand to determine if there is axial run-out on the flange (bent flange from the previous boom). It should be nearly zero. Maybe .001" - check the service manual for the spec.
3. With the same indicator, check the crank thrust end play with a pry bar. The clutch may have damaged the thrust surface on the crank. End play should be .005" - .008" guessing - check the service manual for the spec.
4. Turn the crank by hand, does it feel unusually tight in spots?
5. Drain the engine oil and check for main bearing material in the oil.
6. Inspect the flywheel bolt hole threads for cracks and hole elongation with a long bolt (3"-4" long) of the proper thread size and pitch. A good bolt hole will have a good fit and the long bolt wont wobble much when fully engaged in the treads. You can easily tell a good bolt hole from a bad one using a 3-4" long bolt as a gauge.

If all that checks good, put in a new clutch/flywheel that is precision balanced, using ARP hardware.

SG4247

Pretty much on point!

aireoh · 01-07-2018, 11:53 PM

Quote:

Originally Posted by SG4247

Hard to tell much from the pics, but here is what I would do:

1. Pull the spark plugs.
2. Use a stone and buff off the burrs on flange until it is flat. Put a dial indicator on the rear crank flange face and turn the crank by hand to determine if there is axial run-out on the flange (bent flange from the previous boom). It should be nearly zero. Maybe .001" - check the service manual for the spec.
3. With the same indicator, check the crank thrust end play with a pry bar. The clutch may have damaged the thrust surface on the crank. End play should be .005" - .008" guessing - check the service manual for the spec.
4. Turn the crank by hand, does it feel unusually tight in spots?
5. Drain the engine oil and check for main bearing material in the oil.
6. Inspect the flywheel bolt hole threads for cracks and hole elongation with a long bolt (3"-4" long) of the proper thread size and pitch. A good bolt hole will have a good fit and the long bolt wont wobble much when fully engaged in the treads. You can easily tell a good bolt hole from a bad one using a 3-4" long bolt as a gauge.

If all that checks good, put in a new clutch/flywheel that is precision balanced, using ARP hardware.

SG4247

i’ll give this a try tomorrow brother.

aireoh · 01-07-2018, 11:54 PM

i still have to remove the 4 broken bolts in the crank.
which will take more than just a day.

xsamis · 03-06-2018, 09:06 PM

Im late to the party but i agree with whoever said throw that spec garbage out, its legit trash, had it in a previous car of mine and it was not a quality part, blew my trans/caused excess wear, and i baby'd it, they're a garbadge company too

aireoh · 01-15-2019, 03:35 PM

hey guys, I know i'm a whole lot of late to the party...
I ended up buying a used motor with 1k miles out of a Q50.
Swapped over everything and motor turned out to be good for the remaining of the time I had the Z.
May 15, 2018 wrecked the Z, ended up flipping downhill, I survived.
Bought a CTS-V Sedan for Christmas.
CHEERS.

01-06-2018, 02:33 AM	#1 (permalink)
aireoh Base Member Join Date: Jan 2016 Location: Yuma, Arionza Posts: 32 Drives: 2012 370Z Base 6mt Rep Power: 9	Loose Flywheel, Crankshaft done for? Alright guys, i need some advice. Before i start off, i'll list the mods that could be causing the following problems: JWT CAMS SPEC TWIN DISC CLUTCH & LIGHTWEIGHT FLYWHEEL STILLEN LIGHTWEIGHT UD PULLEY April 15th, 2017 So about a half a year ago, my flywheel came loose. Only reason i figured it was that was because it was chattering way beyond normal flywheel chatter. So i removed it, i had to pry it off 'cause it was literally melted onto the back of the crankshaft. I ran into a problem when i removed it... One of the flywheel bolts had snapped inside one of the crankshaft bolts. I tried everything in my power at the time to remove the broken stud, but i couldn't. So i reinstalled my new clutch and flywheel with just 7 out of the 8 flywheel bolts. September 6th, 2017 The car ran perfectly fine, put over 10k miles on it. I was driving from CA to AZ, when another Z caught up to me in the middle of the dessert, and he started slowing down next to me so i gave him a 40mph in 2nd gear. As soon as i shifted into 3 gear and left off the clutch, i heard a huge explosion. Whatever happened underneath claimed my transmission, transmission input shaft, slave cylinder, pressure plate, clutch, headers, A/F sensors, test pipes, steering column and starter connector. What was untouched was the flywheel, it was still attached to the crank with all of the original 7 of the 8 bolts. Nevertheless, i removed everything cleaned what i could, bought new parts... I ended up spending a little under $5,000. I reinstalled the clutch and flywheel with only 7 of the 8 bolts again 'cause the old flywheel was solidly attached when i removed it. It must've been something behind the flywheel that malfunctioned and just detonated inside my tranny bell housing. November 1st, 2017 I'm driving in Cali i feel the clutch pedal abnormal vibrating with every shift, and just cruising. I take a wild guess and say it's something drivetrain related. So i drive back home to Arizona, knowing i'm taking a huge risk. I remove the transmission when i get home and what do i find? Everything is fine BUT the new flywheel. i remove the pressure plate just to find that 2 more bolts are snapped inside the crankshaft to make it a total of 3 studs stuck in the crankshaft. Circled in red is the original stud i tried removing from back in April. At this point i've had enough, i bought some gold tipped drill bits and do what i can to remove the studs. Long story short, i removed all of the studs that were stuck in the crank. Here's the crank with all of the studs removed. Reinstalled Flywheel and clutch with all of the 8 bolts. I cleaned and retapped every bolt hole just to make sure the bolts would fit perfectly. I sanded the back of the crank down to where everything was smooth and the flywheel would sit flush. Torqued & Locktite was applied. January 1st, 2017 I feel the same vibration i felt two months ago. I say to myself, okay it's gotta be the flywheel again. I ignore it to see if it would go away... I was wrong, the chattering got really bad, like back in April to the first occurrence. So i drove back to AZ on January 3rd, 2017. I just finished pulling the transmission yesterday, and just like i suspected... The flywheel was hanging on by literally a thread.. how did i make it back? I have no clue, but it was stupid driving it such a long distance, i know. I literally shook the flywheel twice and it came off, pressure plate, clutch and all. And come to find that there are now 4 broken studs in the crank. I'm at the point where i don't know what the best option would be. 1.) Pull motor, replace crankshaft. 2.5k. (Since this motor has JWT cams) 2.) Buy a used motor and have it fully replaced for 2k. 3.) Buy a brand new motor and have it fully replaced for 3k. 4.) Drill out studs, buy ARP bolts and locking washers and reinstall the same clutch kit. The Z as she sits now. Please send help. Last edited by aireoh; 01-06-2018 at 02:39 AM.

01-06-2018, 07:14 AM	#2 (permalink)
Chuck33079 A True Z Fanatic Join Date: Nov 2011 Location: Houston Posts: 12,265 Drives: 2011 370ztt Rep Power: 29538	Whatever you do, get rid of the Spec garbage. I don't know if it caused all that destruction, but it sure didn't help. ZontheRocks likes this. __________________ 2011 MB Touring-Sport-6sp-Nav/GTM TT/FI TT TDX/JTran/Kosmic/Eibach/Hotchkis/SPC/CSF/RPS/SoThatsWhereAllMyMoneyWent

01-06-2018, 07:56 AM	#3 (permalink)
SouthArk370Z Premium Member Join Date: Nov 2010 Location: South Arkansas Posts: 8,435 Drives: 2014 Challenger Rep Power: 324197	You made several unsuccessful repairs. Either: A) You don't have the resources to do the repair properly or B) The crank is beyond repair If it's A, then a good machinist will be able to fix it If it's B, then a good machinist will be able to tell you. Find a good machinist and get their opinion. I'm betting that the crank is trashed. Your option 4 sounds like the worst possible thing to do - you haven't fixed the root problem. Chuck33079 and ZontheRocks like this. __________________ Steering Lock Links - Search The370Z Bookmarklet - FSM @ NICOclub Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma

01-07-2018, 05:42 AM	#7 (permalink)
SG4247 Track Member Join Date: Oct 2016 Location: OKC Posts: 723 Drives: 2010 touring Rep Power: 4486	Hard to tell much from the pics, but here is what I would do: 1. Pull the spark plugs. 2. Use a stone and buff off the burrs on flange until it is flat. Put a dial indicator on the rear crank flange face and turn the crank by hand to determine if there is axial run-out on the flange (bent flange from the previous boom). It should be nearly zero. Maybe .001" - check the service manual for the spec. 3. With the same indicator, check the crank thrust end play with a pry bar. The clutch may have damaged the thrust surface on the crank. End play should be .005" - .008" guessing - check the service manual for the spec. 4. Turn the crank by hand, does it feel unusually tight in spots? 5. Drain the engine oil and check for main bearing material in the oil. 6. Inspect the flywheel bolt hole threads for cracks and hole elongation with a long bolt (3"-4" long) of the proper thread size and pitch. A good bolt hole will have a good fit and the long bolt wont wobble much when fully engaged in the treads. You can easily tell a good bolt hole from a bad one using a 3-4" long bolt as a gauge. If all that checks good, put in a new clutch/flywheel that is precision balanced, using ARP hardware. SG4247 Trips, SouthArk370Z, Memphis370Z and 3 others like this. Last edited by SG4247; 01-07-2018 at 05:57 AM.

01-07-2018, 11:54 PM	#10 (permalink)
aireoh Base Member Join Date: Jan 2016 Location: Yuma, Arionza Posts: 32 Drives: 2012 370Z Base 6mt Rep Power: 9	i still have to remove the 4 broken bolts in the crank. which will take more than just a day. __________________ FBO, Cammed, E85, 12.6 1/4 mile

03-06-2018, 09:06 PM	#11 (permalink)
xsamis Base Member Join Date: Sep 2017 Location: MI Posts: 75 Drives: 2011 nissan 370z Rep Power: 7	Im late to the party but i agree with whoever said throw that spec garbage out, its legit trash, had it in a previous car of mine and it was not a quality part, blew my trans/caused excess wear, and i baby'd it, they're a garbadge company too ZontheRocks likes this.

01-15-2019, 03:35 PM	#12 (permalink)
aireoh Base Member Join Date: Jan 2016 Location: Yuma, Arionza Posts: 32 Drives: 2012 370Z Base 6mt Rep Power: 9	hey guys, I know i'm a whole lot of late to the party... I ended up buying a used motor with 1k miles out of a Q50. Swapped over everything and motor turned out to be good for the remaining of the time I had the Z. May 15, 2018 wrecked the Z, ended up flipping downhill, I survived. Bought a CTS-V Sedan for Christmas. CHEERS. jae35 and wideglideleon like this. __________________ FBO, Cammed, E85, 12.6 1/4 mile Last edited by aireoh; 01-15-2019 at 03:48 PM.

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