Crank to Flexplate bolts keep backing out

Back when mine was doing that Brandon I used the longer bolts I sourced from Mumau, but it sounds like you may have a different issue?


To everyone saying the ATI damper is the problem, why did his 12v never have this problem? That damper has been on his engines for years now
Chris
 
To dump 12 pounds off the crank you would most certainly be into the fly weight that counter's the torsional pounding diesel's make. Remove all the fly weight and at high rpm you couldn't keep a damper or fly wheel on the thing. Crankshaft wouldn't likely survive either at any significant power level either.

That said we always torque turn the flex plate/damper bolts. Almost certain what we do has to be yielding more than 105 ft lbs.
 
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It did it with brand new bolts from Cummins and a brand new flex plate. Based on the guesses here, I'll be swapping out to a factory damper. I have one, now it's a matter of getting the truck in the shop and swapping it out. Glad I put Dzus fasteners on the front clip this year. :rockwoot:
 
What is the TTY spec for thee crank bolts? I can only find the 95 ft/lb spec.
 
I'm not sure the factory dampener will be much better with the change in rotating weight. Fluidampr may be your best bet for a "fits all" approach. You could likely just give ati the new weights and rpm range and they may adjust the current one to match.
 
I thought I-6 cranks had a natural internal-balance meaning the flexplate and balancer are a neutral balance?? Did knocking 12lbs off the crank now turn this into an external balance requirement, bob weights, flex plate, balancer type balance? V8 style balance?
 
SoDak24valve said:
If the shop that removed the weight from the correct areas on the crank and spent the time to balance it correctly the crank won't be the issue. Also I have yet to have any issues with any ATI damper I have installed and used. One of my trucks also has weight removed from the crank and running a ati as well, I have swapped two different tranny set ups in it over last summer and never had an issue with anything coming loose or breaking due to a damper or weight reduction of the crank.
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Signature600 said:
Back when mine was doing that Brandon I used the longer bolts I sourced from Mumau, but it sounds like you may have a different issue?


To everyone saying the ATI damper is the problem, why did his 12v never have this problem? That damper has been on his engines for years now
Chris
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Proving something doesn't cause a problem is very difficult. I think the folks who have experienced these issues are saying it could be the ATI because they have experienced it actually being the cause of these symptoms.
 
joefarmer said:
What is the TTY spec for thee crank bolts? I can only find the 95 ft/lb spec.
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22 ftlbs + 60 degree turn. I don't have anything handy or on a stand to see how that compares to a basic ftlbs but by memory sure seems like it feels more than 95. Never use locktite either.

Damper 30 ftlbs + 60 degrees.
 
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The whole issue is they are related. I had loose flexplate bolts(operator error of torque wrench LOL) and I couldn't keep the fluid damper tight(even with a pin kit). Tightend the flexplate bolts up and the damper quit loosening.
 
2 weeks before mine came apart, i was talking to a fluid damp rep, he told me about issues with the ati damper... He knew i was running one, and actually gave me a brand new one to install when i could.. Talking about timing huh... The truck is hands down more quiet, and smoother running cause of it..after mine sheared apart i looked on the internet, and there was alot of these story's around.. Wtf.
 
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Did you ever measure the bolts to see if they had stretched, or just vibrated out? Lock wire would help if its vibrating, but if they are stretching, it'll still loosen up.
 
Tate said:
Did you ever measure the bolts to see if they had stretched, or just vibrated out? Lock wire would help if its vibrating, but if they are stretching, it'll still loosen up.
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I didnt measure the bolts... Couldnt find any lol..
 
Brandon, I'd almost be worried about the outer ring getting flung off a stock one if there are some bad harmonics and compounded with the higher rpm.
 
Joesixpack said:
22 ftlbs + 60 degree turn. I don't have anything handy or on a stand to see how that compares to a basic ftlbs but by memory sure seems like it feels more than 95. Never use locktite either.

Damper 30 ftlbs + 60 degrees.
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22 and 60 is 110
 
97rada said:
22 and 60 is 110
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Good to know. My elbow torque wrench firgured it was more than 95. (Always just use an old school degree dial and a flex handle) rather than one of these fancy pants digital degree wrenches that's on my Santa list.
 
Joesixpack said:
Good to know. My elbow torque wrench firgured it was more than 95. (Always just use an old school degree dial and a flex handle) rather than one of these fancy pants digital degree wrenches that's on my Santa list.
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That's what rockers on an Isx tq to. Only reason I know. Tq turns are pricy
 
97rada said:
That's what rockers on an Isx tq to. Only reason I know. Tq turns are pricy
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Depends on the length of the bolt. The longer the bolt, the lower the equivalent torque will be per degree. Those numbers are only accurate if the rocker bolt and damper bolts are the same effective length.
 
Hold the phone there, are those the same size bolt and thread pitch? Don't think you could make the correlation otherwise.

Edit: Got tree'd there damnit.
 
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