Broken Crankshaft Count?

[LBZ]

Just through a couple gm techs I know personally, in the last 4 years I can say there was 1 with an edge and 10 maybe 12 that were stock. Most were lbz/lmm. And that's just 2 guys at one dealer.

 

[Gil714]

One of the interesting things that I've haven't seen done yet is have someone design a front crankshaft support for these motors. Moreover, it seems that GM could consider going to a non-twist forging for the cranks.

 

[LBZ]

I believe supports have been built and used by some pullers.

And cost along with the fact gm has not had many cranks break under warranty are possibly why they haven't made any changes in their design.

 

[new york lly]

http://www.duramaxdiesels.com/forum/showthread.php?t=69122&highlight=2007+classic+Chevy+2500HD+ecsb

Bought this truck mid January put 2000 "normal" miles on it,started making some racket like the fan was catching on the shroud. Took a look & could see the balancer wobbling....Had a local shop ck it out said the crank was broke..put it on truck & had it shipped to Mark & Larry @ Danville

 

[WVRigrat05]

That ****in blows, I would have puked.

 

[new york lly]

That ****in blows, I would have puked.

Awe man you have no idea!!!! Just responding right now is making my heart race!!! Just got word today that it's @ Danville, it's weird cuz I'm really excited to have those guys build it but I'm sick cuz I shelled out a ton a dough on a truck that I thought was good to go... Gonna put an AF cam in it this time...

 

[WVRigrat05]

I can only imagine.
Are you going with a new crank or used?

 

[new york lly]

I can only imagine.
Are you going with a new crank or used?

Well talkin w/ Larry it appears to be a $400 swing between used & new stock keyed so I am for sure going new...or I can go w/Billet for $5K haha yeah rt!

 

[WVRigrat05]

Billet parts prices are nuts depending on the part. 400 bucks is a cheap price of mind for sure.

 

[new york lly]

Billet parts prices are nuts depending on the part. 400 bucks is a cheap price of mind for sure.

I think it is...the AF cam as well...I'm a little concerned about the turbo's I talked w/ the fella I got the truck from & he said his sons LBZ just broke a crank & wrecked the turbo...I hope I shut it down in time the truck was still running...I'm sure Mark will let me know

 

[WVRigrat05]

I hope mine doesn't break, at least until oil prices start climbing. I still keep going back and forth on getting rid of my truck it's got 70k on it as of yesterday so it's only a matter of time before the nickel and diming begins.

 

[new york lly]

I'm @ the point of no return haha!! I got to much into it now just gotta get it rt & make it where its dependable....I really confident that DP can do that for me:thumb:

 

[WVRigrat05]

Yeah, once you're in it, your in it. Danville does great work, you're def. in good hands.

 

[new york lly]

Really couldn't find anyone local that has performance Duramax experience in fact the shop that diagnosed the truck said they could throw a crank in it but really didn't want me coming back in 6 mos w/the same issue....they were pretty straight about not knowing enough as to why these trucks break cranks,I really appreciated their honesty.I really liked the idea of Danville doing the work cuz they tuned the truck to begin with...so I guess the deciding factor was the cost to ship the truck to Danville...it seemed like a no brainer.....

 

[Maxhdcrew]

I've been reading this entire post as I just picked up a complete lb7 that had a broken crank at the second journal for cheap in hopes the block is good and I can start building a new motor for my truck. I've been doing a lot of thinking, assuming, and using my knowledge from all the racing and motor building we've done over the years, ( dad owns a machine shop). Most guys have just had them break at low rpms, which made me think. If the alternate firing order cam is helping then it has got me leaning towards an imbalance in combustion pressure. It's taking too long before a balance of explosion onto the other bank further back to keep the rotating assembly rotating smoothly. Poor intake design, insufficient intake flow, too much timing and poor cylinder balancing. The engines with injectors that are very poorly balanced from Bank to bank would speed this havoc up tremendously coupled with all the other short coming of the intake system. I feel that the AF cam just helps to balance out the press on the rotating assembly, but could the problem be stemming from poor intake balancing and then you throw in imbalanced injectors also(poor filtration, lack of maintenance ) with the 1,2 hit on the weakest part of the crank and there's the perfect storm for a 2 piece crank..... do you guys think the balancing act with the injectors is kind of a bandaid to the harmonics issue and poorly balanced intake design. It worked good enough to alleviate a majority of the harmonics so they used it? Most of you know more than I do but these were some things I thought about. Does any of it hold any water?

 

[malibu795]

Ive broken two cranks two different ways.. One was a spun #2 main(lb7 flooded crankcase with fuel), latter was sheared 5mm dowl pin for the crankshaft reluctor wheel..at less than 2000rpm

My question is how many crankshaft actually broke do to shear force and not some other contributing factors? Ie bearings/dowl pin failer

 

[56taskforce]

I've been reading this entire post as I just picked up a complete lb7 that had a broken crank at the second journal for cheap in hopes the block is good and I can start building a new motor for my truck. I've been doing a lot of thinking, assuming, and using my knowledge from all the racing and motor building we've done over the years, ( dad owns a machine shop). Most guys have just had them break at low rpms, which made me think. If the alternate firing order cam is helping then it has got me leaning towards an imbalance in combustion pressure. It's taking too long before a balance of explosion onto the other bank further back to keep the rotating assembly rotating smoothly. Poor intake design, insufficient intake flow, too much timing and poor cylinder balancing. The engines with injectors that are very poorly balanced from Bank to bank would speed this havoc up tremendously coupled with all the other short coming of the intake system. I feel that the AF cam just helps to balance out the press on the rotating assembly, but could the problem be stemming from poor intake balancing and then you throw in imbalanced injectors also(poor filtration, lack of maintenance ) with the 1,2 hit on the weakest part of the crank and there's the perfect storm for a 2 piece crank..... do you guys think the balancing act with the injectors is kind of a bandaid to the harmonics issue and poorly balanced intake design. It worked good enough to alleviate a majority of the harmonics so they used it? Most of you know more than I do but these were some things I thought about. Does any of it hold any water?

Poor intake balance is what Gail Banks think's :hmm:

 

[malibu795]

Poor intake balance is what Gail Banks think's :hmm:

He alson increased main bearing diameter on his crankshaft

 

[hondarider552]

If #1 main used a wider bearing like the block has room for I bet that would help, but probably not:spit:

 

[56taskforce]

What the hell is that supposed to mean Brian??? (((Could be but probably not))):roflmao::hug: