Broken Crankshaft Count?

[ikeG]

Several billet cranks broke at the limited pro stock power level this past pulling season. This is an assumption, but given the caliber of the builds, it's a safe bet they were narrow rod, internal balance, and/ or at very least, AF cams. Talking 1300-1400 hp.

Sent from my SM-G960U using Tapatalk

 

[Evan@InglewoodTrans]

I would be willing to bet that most every broken crank that was internally balanced wa well in excess of 1000 hp and broke farther to the rear.
Every thing has its limits, how many examples here have been internal balance shafts?
I am currently not disputing you Even in fact I have the utmost respect for your experience, knowledge and contributions to this community. Here I believe we may be moving beyond one issue and in to another and I certainly hop I am not wrong and I am tying up a lot of money in a build banking on it

Your statement was that the combo would solve the problem not that it would solve up to a 1000hp. A 1000hp is almost normal these days. Every COMP trans I’ve built over the years had been bolted to a strong running engine and any time there is a failure on any sort on the truck I’m involved with I hear about it. Running a alt cam with internal balancing has been done for years and there is still failures and not just further back. 100’s and 100’s of built motor truck owners never grace the internet with there experiences and I’m sure if you can get some engine builders to be honest they can tell you the same thing. If the fix was that simple you’d of known about it years ago. I’m sure someone will be able to provide with some pics I only have pics of transmission failures that supposedly can’t happen

 

[juddski88]

Wonder why they dont make a viscous filled 80 lb flywheel to help with the bal , never mind I just figured it out myself , because every time you would start the eng the viscous material would have to rebalance , thus damaging the eng bearings a little on each startup .

In an auto trans setup, you essentially have a type of 80 lbs viscous damper on the rear. It's not hanging, the intent is to keep it well supported and properly aligned. But in keeping with that thought, what happens on the driven end of the engine has a pretty large impact on the rotating assembly.

 

[kidturbo]

Several billet cranks broke at the limited pro stock power level this past pulling season. This is an assumption, but given the caliber of the builds, it's a safe bet they were narrow rod, internal balance, and/ or at very least, AF cams. Talking 1300-1400 hp.

Sent from my SM-G960U using Tapatalk

Somebody actually confirm breaking an Ultrabillet?

Mine are about 3yrs old and haven't rusted in half yet from lack of use. Not to say they won't snap one day, because I completely agree with Mark on the root cause. However the higher grade material should yield some better longevity, one would expect.

Far as harmonic vibrations goes, the 240ish pounds of rotating mass with half a gram tolerance across the board theory that I'm chasing, runs like a sewing machine under 1000hp so far.



Sent from a reclined position using Tapatalk

 

[Chevy1925]

Several billet cranks broke at the limited pro stock power level this past pulling season. This is an assumption, but given the caliber of the builds, it's a safe bet they were narrow rod, internal balance, and/ or at very least, AF cams. Talking 1300-1400 hp.

Sent from my SM-G960U using Tapatalk

are these trucks running direct drive/clutches or still an auto with converter attached? stock blocks?

 

[ikeG]

are these trucks running direct drive/clutches or still an auto with converter attached? stock blocks?

3 or 4 disk clutches with single speed direct drive transmissions. Stock block required in that class.
We got out of it in 2018, I now know just the highlights. Won't/can't comment on who.

Sent from my SM-G960U using Tapatalk

 

[Dozerboy]

Y’all and your honesty are a bummer. I thought the narrow journal crank would do it. Well I have no plans to exceed 1000hp, so maybe I’ll luck out.


Sent from my iPhone using Tapatalk

 

[Chevy1925]

They are at the limits of the stock block. its hard to say that isnt moving around, putting undo stress on the crank and causing it to snap/fatigue over time. Sled pulling setups like Ike gave is EXTREMELY hard on the drivetrain. there is no give any parts. while an auto under lockup should have "no give", you still have longer smaller shafts in there that will twist and give more so than these trucks see.

As you fix one problem or strengthen one, you move the next weak point farther up the line.

i would be curious if they used a custom thick front and mid mount engine mount setup with an integrated girdle how that would work for them. It may be time the crank mfg look into building an L5P style crank and use carrillo L5P rods on it. that moves the rod to main overlap in a more favorable position and puts more meat on the bones than a narrow rod.

im also curious as to what crank it was that failed. Guys cranks are .250 narrowed, callies are .050 narrowed. thats a big difference.

 

[ikeG]

I just confirmed a couple things from a buddy that did break one. He broke a billet stroker Winberg at the rear. He is unsure if narrowed journals but they do run aluminum rods. Built by wagler. He confirmed that another wagler customer broke at least two, unsure on location but assuming the same crank.
He is also aware of someone else breaking a billet but no other details.
Common denominator that we can be sure of is big heavy clutches. And solid front/mid plate engine mounts

Sent from my SM-G960U using Tapatalk

 

[MarkBroviak]

In the 13 years of being in the Dmax game I can tell you right now it is a design issue pure and simple. We have tried pretty much every single combo you could. Only the SoCal and Callies Ultra Billet haven't failed us yet in this manner. Both aren't that old so time will tell in the long run. Internal balance with or with out fluidampner. ati, socal balancer, clutch or auto, aluminum rod vs. steel rods, stroker vs stock stroke(destroked haven't seen anything there mainly because there aren't many out there but that crank should be stronger yet since it has more pin overlap) still have failed. Here is the part being over looked, if it was a power issue then you would have bent the crank and damaged the bearings and 99% of these failures don't have those issues to go along with the broken crank. Stock block design is only good for up to roughly 1400hp before you start splitting cylinder walls full filled or not! Motor mounting location and process is harder on the block itself than it is the crank. If it is flexing enough to affect the crank you will wipe the bearings out first, or you should at least. Ken is right, more weight hanging off the crank the smoother it operates but it is just because the mass is absorbing it, the harmonics is still being produced. The Cummins guys definitely have it easier than us in this respect but I would still rather push my Dmax than drive a 6cylinder, lol!

 

[buick455]

I personally know of a 3.6 truck that has fractured numerous stock cranks and broken 2 Winberg cranks. The stock cranks were when it was 3.0 grooved. For the last 2 seasons it's had a Callie's Ultrabillet and no issues. I agree with Mark on there is an overall underlying issue but this does show something good for the Ultrabillet as well as no "online" known failures. My thought anyways.

 

[MaxPF]

In the 13 years of being in the Dmax game I can tell you right now it is a design issue pure and simple. We have tried pretty much every single combo you could. Only the SoCal and Callies Ultra Billet haven't failed us yet in this manner. Both aren't that old so time will tell in the long run. Internal balance with or with out fluidampner. ati, socal balancer, clutch or auto, aluminum rod vs. steel rods, stroker vs stock stroke(destroked haven't seen anything there mainly because there aren't many out there but that crank should be stronger yet since it has more pin overlap) still have failed. Here is the part being over looked, if it was a power issue then you would have bent the crank and damaged the bearings and 99% of these failures don't have those issues to go along with the broken crank. Stock block design is only good for up to roughly 1400hp before you start splitting cylinder walls full filled or not! Motor mounting location and process is harder on the block itself than it is the crank. If it is flexing enough to affect the crank you will wipe the bearings out first, or you should at least. Ken is right, more weight hanging off the crank the smoother it operates but it is just because the mass is absorbing it, the harmonics is still being produced. The Cummins guys definitely have it easier than us in this respect but I would still rather push my Dmax than drive a 6cylinder, lol!

From the sounds of it, DMax guys get plenty of opportunities to push or tow their junk :roflmao:

 

[kidturbo]

Luckily not as quite as much Dodge guys need to, ever since they dropped the manual trans option...

Sent from a reclined position using Tapatalk

 

[56taskforce]

Or from just the truck falling apart around the Cummins
!!! But that's a good thing for Ford owners as it leaves good Cummins motors for them to swap in LOL They all have their pit falls, what is it they say tires or tits??? Even with the crank issue Duramax is still on top for reliability. Maybe a built in problem to keep up the friendly rivalry :roflmao:

 

[MaxPF]

Or from just the truck falling apart around the Cummins

Hate to break it to you, but that is the case for all vehicles nowandays. They're all disposable junk with 20 year lifespans.


My gripe with the DMax is that a crankshaft is just not an item that should never fail in a stock truck. They look barely larger than an LS crank. The Ford 6.7 crank isn't much different, but Ford has deep pressure-rolled fillets on their cranks. Those are known to be superior to even wide radius fillets for preventing the initiation of fatigue cracks at the journal cheeks. Why GM dodn't do that on the DMax crank when they DO use rolled fillets on the gasser cranks is beyond me.


Here's the Ford 6.7 crank:

The International 6.0 and 6.4 also had rolled fillets on the mains and rods:

In case anyone thinks maybe they forgot, remember the old 6.2L IDI diesels? They had rolled fillet nodular cranks ever since they debuted in 1982:

It also shouldn't have taken GM this long to fix the known crank breaking problem. Assuming it's fixed in the L5P

 

[Chevy1925]

the rarity of a stock crank breaking in a stock truck is very high. blows the 68rfe out of the water for failure rate along with the turbos or HG that like to say bye bye on newer cummins. lets not forget the shitastic front ball joints and factory installed death wobble.

its not the fillets that are the issue, aftermarket cranks tried it. its the lack of overlap on the rod journal to main journal. the .200 larger radius in the L5P "should" stop the issue. the narrowed rod journal in some aftermarket cranks is showing promise as well.

 

[MaxPF]

Ahh yes, the Duramax crankshaft. At least this one is still in one piece! :roflmao:

Look at the fillets:

One thing that is obvious is that not only is the radius not particularly wide, but it isn't even finish ground. that leaves a small discontinuity with a circular lay that makes a nice stress riser.




Let's look at a Cummins crank:

Note that this extremely manly piece of forged steel was designed for an engine that topped out at 160HP and 400lb/ft or torque in it's initial incarnation. It's not noticeable in this crank, but the journals on all Cummins cranks are induction hardened before finish grinding. On many cranks you can see the rainbow discoloration on the arms opposite the journal side.


Check out the fillets:

The fillets have a much wider radius vs the DMax crank, and they are finish ground to top it off. No stress risers. Keep in mind this is a 4.72" stroke crank, and the 6.7 crank is 4.88" stroke. Main journals are 3.268" diameter, and the rods are 2.717". The thick arms between throws definitely doesn't hurt either. I think with a few changes the pre-L5P engines wouldn't have had crank issues, at least at stock HP/tq levels, say current L5P power levels. After all, plenty of 6.0 and 6.4 Ford guys made more than that on a routine basis, and if they kept head gaskets intact they didn't have crank issues. Which is impressive since the International cranks look puny even compared to the Duramax crank. Well, until you look at the diameter and overlap of the 6.0/6.4 main and rod journals. The rolled fillets definitely don't hurt either

 

[ikeG]

Worst one I've had.

Source: https://youtu.be/LERYTV5rxoU

Lmm. Both crank pins sheared, 8 valves total hit pistons. Appears to have had a recent head gasket job too.

Sent from my SM-G960U using Tapatalk

 

[kidturbo]

Saw this one couple days ago and had to share it. It knocked, wobbled, but had no movement when pry bar was used to check it.

Well there's your problem..

Sent from my SM-G892A using Tapatalk

 

[56taskforce]

Did te block survive? Looks like it was caught just in the nic of time for the possibility...