Broken Crankshaft Count?
- Thread starter EDP
- Start date
I can add a couple cranks i know of one in an lbz and one in an lmm tow truck. The lbz broke at 5&6 and the lmm broke at 3&4.
<Moose>
<Moose>
My friend who does some failure analysis for cat looked at mine, said that it had been cracked for quite a while. He said the section of break that is more polished has been that way a long time and the rough ridges were more recent.
add an lly to the list bent .004 in v blocks, contributing failure high oil temps and oil breakdown. found on yearly teardown of engine for measurement and inspection
here are some pics and a link to bearing analysys
http://catalog.mahleclevite.com/bearing/
thinking the fix is more support at the #2 main.
http://catalog.mahleclevite.com/bearing/
thinking the fix is more support at the #2 main.
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03 Lb7 manual trans, engine all stock, crank it up tunes, fuel system and dual disc clutch. cruising 60 mph down the highway.
bummer 
More LB7/LLY's on the list than LBZ/LMM's... guessing only because there are more LB7/LLY owners?
More LB7/LLY's on the list than LBZ/LMM's... guessing only because there are more LB7/LLY owners?
Possible?
Hey guys been a while since ive been on but as i just today had my second STOCK lmm broken crank pull into the shop and both cases had recently had loose balancers due to piss poor workmanship on water pump installs, kinda makes me wonder if there is something to that. any of these broken cranks fall not long after water pump install????
Hey guys been a while since ive been on but as i just today had my second STOCK lmm broken crank pull into the shop and both cases had recently had loose balancers due to piss poor workmanship on water pump installs, kinda makes me wonder if there is something to that. any of these broken cranks fall not long after water pump install????
One major contributer has already been proven to be any unstable harmonics....from tuning, to poor balancing, to chowdering out on a balancer bolt...ultimately they can all cause the same thing.
Yes there is something to it.
As you know balancers on these rigs are not light, if you have a loose balancer hanging off the end of the crank, especially driving all belt driven accessories, that is a ton of unbalanced force on the end of a lever pounding away. While I don't believe it's the only reason cranks break, it's a good recipe for a broken one (especially on a completely stock motor where there "shouldn't" be any issues).
I know this is WAY out there...
Has anyone ever thought that the Duramax tick/knock might have a hand in this? I was told the tick/knock was the result of an oil film condition between the crank and the main bearings. Maybe it is causing premature wear, I was told that it comes from tiny air bubbles trapped in the oil. Air does not lubricate very well. And some duramaxes tick/knock way more than others, so that maybe the answer to why some break and some don't...
Has anyone ever thought that the Duramax tick/knock might have a hand in this? I was told the tick/knock was the result of an oil film condition between the crank and the main bearings. Maybe it is causing premature wear, I was told that it comes from tiny air bubbles trapped in the oil. Air does not lubricate very well. And some duramaxes tick/knock way more than others, so that maybe the answer to why some break and some don't...
I was wondering if anyone had been using a girdle or not. You would think tying the main caps and oil pan rail together would stiffen the whole thing up quite a bit. A girdle distributes the load throughout the block instead of letting it concentrate on the individual main webs. When I finally do my engine build a 14mm girdle, Xxl studs, billet caps, and new balanced crank are gonna be a must. I know a lot of these cranks have been on stock trucks but the built motors are what I don't understand. Not replacing the crank and reinforcing it someway under high hp doesn't make sense to me I understand money is a big factor but why not beef up the most important part. (That would be like rebuilding a trans and not replacing a couple clutches just because they don't look that bad.) :roflmao: If your going to rebuild something might as well freshen it all up. You don't want to have to tear it all back apart cause you didn't take extra precautions before. I would understand if it's all up to spec but why risk such an important part.
I also agree that regular maintenance needs to be done also. Once oil has done gotten hot too many times it oxidates, breaks down and then becomes acidic. doesn't matter if it is the best oil money can buy. But that's my opinion.
I also agree that regular maintenance needs to be done also. Once oil has done gotten hot too many times it oxidates, breaks down and then becomes acidic. doesn't matter if it is the best oil money can buy. But that's my opinion.