Broken Crankshaft Count?

Please pick the one that you had break


  • Total voters
    185

DIGGLER

Member
Feb 6, 2011
94
0
6
SC
im not saying the oil temping issue is not causing crank breakage, but it still isnt a solid thing for me. i work on alot of abused stuff, and for the most part, as long as there is oil in the engine with decent pressure, it's pretty much going to be ok. ive drained pure transmission oil out of engines, and engine oil out of transmissions. a broken crankshaft just doesnt happen very often in anything but the duramax engines, from what i can tell.
also, an engine that has lost its oil pressure would tend to trash the bearings from metal to metal contact. (there is no film being maintained between the parts)
my bearings all looked fine and yet the crank broke. so, in my mind, the oil pressure didnt drop off in my engine. yours, having spun bearings, could have very possibly had a pressure issue, since the loss of oil film meant your crank journals grabbed the bearings and tried to become one with them.

i just don't know. it is frustrating to not know a solid cause of this. not discounting anything at this point, just trying to reason my way through to a solution.
 

hondarider552

Getting faster
May 28, 2008
10,627
2
36
34
Arizona
in your opinion, how much oil would a stock duramax with no mods or tune need to stay properly cooled?

When I used to work at a diesel shop, a 6.0 ford, 5.9 cummins, and 6.4 pstroke could come into the bay, and I could touch the oil coming out of the pan without burning my hand, never once could I do it with a dmax. IMO, 15 qts. Hell, the Kodiaks are front sump 15 qts IIRC..
 

Bryce418

Still slow
Oct 5, 2009
611
0
0
I tend to agree with Micheal on a larger amount of oil would likely not help oil temps, it would help avoid violent spikes in temperature, but would do little if any good for sustained heat.

I feel a better oil cooling system would have far greater benefits vs probably just adding cost to oil changes.
 

Leadfoot

Needs Bigger Tires!
Dec 27, 2006
904
31
28
48
Western MA
www.matpa.org
I tend to agree with Micheal on a larger amount of oil would likely not help oil temps, it would help avoid violent spikes in temperature, but would do little if any good for sustained heat.

I feel a better oil cooling system would have far greater benefits vs probably just adding cost to oil changes.

Without being able to add a significant amount of capacity (not likely), the easiest solution (as Michael is pursuing) is cooling the existing oil efficiently and before it breaks down. In an ideal world, there would have been more capacity to begin with ALONG with more efficient cooling. It would have been nice if the capacity was in the 12-15 quart range (plus additional for filter). That's not likely to happen, so cooling what is in there is our best solution (not to say some haven't lasted a long time as is, but those temps reported aren't good).
 

super diesel

<<<< Under Pressure
(not to say some haven't lasted a long time as is, but those temps reported aren't good).

Very well put.

It's very clear that GM didn't want to design (or have designed in by Isuzu) the capabilities of a motor that would last a very, very long time (their revenue would suffer from this). Proof positive is the lack of EGT and oil temp gauges. It's a slow burn up (but quickly in some cases).
 

Dave L Weaver

New member
Apr 5, 2011
57
0
0
38
Chester County Pa
lb7 broke

Think i just broke my crank!:( Was driving around 60 mph n had just started getting into the throttle when it popped n rattled n died. The balancer wobbles n you can wiggle it when you pry it. The engine runs smooth...maybe just a little vibration.... What is the chance my block is ok n didn't mess to much up?
 

LBZrcks

.........
Jun 2, 2007
5,297
12
38
38
SoCal
Think i just broke my crank!:( Was driving around 60 mph n had just started getting into the throttle when it popped n rattled n died. The balancer wobbles n you can wiggle it when you pry it. The engine runs smooth...maybe just a little vibration.... What is the chance my block is ok n didn't mess to much up?

:( Sorry to hear
 

hondarider552

Getting faster
May 28, 2008
10,627
2
36
34
Arizona
Think i just broke my crank!:( Was driving around 60 mph n had just started getting into the throttle when it popped n rattled n died. The balancer wobbles n you can wiggle it when you pry it. The engine runs smooth...maybe just a little vibration.... What is the chance my block is ok n didn't mess to much up?

I am sure your block is junk if you were going that fast and it ran for that long.
 

super diesel

<<<< Under Pressure
Think i just broke my crank!:( Was driving around 60 mph n had just started getting into the throttle when it popped n rattled n died. The balancer wobbles n you can wiggle it when you pry it. The engine runs smooth...maybe just a little vibration.... What is the chance my block is ok n didn't mess to much up?


So sorry to hear. I don't want to also bear bad news but I would count on replacing the block unfortunately. Mains are probably shot.
 

Dave L Weaver

New member
Apr 5, 2011
57
0
0
38
Chester County Pa
Well guess we will tear it apart n find out! Its just i only have 20k miles on the build:( The crank does have 350k on so we should have replaced it maybe.... guess we live n learn!!!
 

elvenhome21

New member
Jun 7, 2012
14
0
0
I dont get it, why would the journal with the least amount of torque be the one to consistently snap off. Ive seen a whole bunch of gas race engines shear off at the rear main or center main on a ford 2300, but never on the first journal. Heck ive seen a few balancers come rolling off the snout and the crank is still fine after several laps without it.

I understand the being out of balance but you would literally need the outer part of the balancer spin/slip quite a bit off of zero balance to create that much of a damaging harmonics.
 

blackdirtymax

New member
Apr 15, 2010
825
0
0
augusta, ga
I dont get it, why would the journal with the least amount of torque be the one to consistently snap off. Ive seen a whole bunch of gas race engines shear off at the rear main or center main on a ford 2300, but never on the first journal. Heck ive seen a few balancers come rolling off the snout and the crank is still fine after several laps without it.

I understand the being out of balance but you would literally need the outer part of the balancer spin/slip quite a bit off of zero balance to create that much of a damaging harmonics.

It has do with the weight of the balancer and harmonics , and the distance from the end of the crank to where it snaps . We have alot of crap going on at the front of the cranks of these engines .


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Slammed2007Lbz

Super Spicy Tunaz
Feb 1, 2009
1,118
0
36
NE Ohio
Look how heavy the harmonic dampener is hanging of the front of one of these cranks ;)
Plus i think i read that part of the crank spans the furthest distance un supported. I think some shop came up with some sort of stabilizer to help the issue but not sure on that. I thought i read it on here but who knows lol
 

blackdirtymax

New member
Apr 15, 2010
825
0
0
augusta, ga
Look how heavy the harmonic dampener is hanging of the front of one of these cranks ;)
Plus i think i read that part of the crank spans the furthest distance un supported. I think some shop came up with some sort of stabilizer to help the issue but not sure on that. I thought i read it on here but who knows lol

Yep, if I had to sling that heavy sum- ma-bit around , I would check out also!!


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hondarider552

Getting faster
May 28, 2008
10,627
2
36
34
Arizona
Beach marks... interesting. Wonder how much exactly these cranks flex before they break. How did the mains look on that journal?


Anyone know how much the stock damper weighs compared to others?
 

blackdirtymax

New member
Apr 15, 2010
825
0
0
augusta, ga
Beach marks... interesting. Wonder how much exactly these cranks flex before they break. How did the mains look on that journal?


Anyone know how much the stock damper weighs compared to others?

Brian , I imagine there is alot of deflection in these motors. Probably would scare some to know how much


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Built motor , duel fuelers , 60's overs , gtx4202r