LBZ: Broke my crank
- Thread starter BHoward6.6
- Start date
My ? is .... :thinking2:
How many of these failures have had a balancer shear the pin in the past and spun the balancer on the crank ?
I have a crank here LB7 .... that is broke at 2nd journal and it sheared the pin and spun the balancer . Its from the block I am using now .
Very common for a dmax to break the crank in this situation with a spun balancer .
I spun a balancer on my new motor shortly after the build .... dealer left the crank bolt loose after doing a water pump . That was the ultimate SUCKY DEAL ! .... fresh motor all balanced and you shear a crank pin due to neglagence from another . Sheared it on the throttle in 4th gear ..... shook like a son of a bitch . So much for a socalled balanced motor .
Always in the back of my mind ... fatigue from this in the past .
BHOWARD .... so sorry to hear your luck brother . Hadnt heard you broke the truck . So how is the new motor coming along ?
The Pin to balancer relationship was good, pin was straight.
Hate to bring up a old thread, but I have been searching forever on answers from other people with this issue. I broke my lbz crank a few months ago I still yet to pull the motor to see the damage but mine broke just cruising at about 40 mph on very conservative tuning too. I'll be posting pictures soon when I pull the engine. The thing that worries me is that it happens for to rhyme or reason so what's to say with another crank the same thing won't happen again( because that's the luck I would have)
It's the SoCal Diesel stage 2 motor I bought from cuminstrkmydmax in Jan.
It has the #6480 (hot street/tow) cam, crower rods, cut & coated pistons, Billet mains, Chrome-moly pushrods, stage 2 heads with titanium retainers,
70% injectors, PPE duel fuelers, and a 4094 va with a s475.
MA solid motor mounts and over-flow tank (degas tank).
It has the #6480 (hot street/tow) cam, crower rods, cut & coated pistons, Billet mains, Chrome-moly pushrods, stage 2 heads with titanium retainers,
70% injectors, PPE duel fuelers, and a 4094 va with a s475.
MA solid motor mounts and over-flow tank (degas tank).
Attachments
Basically the same symptoms as I had except for the boost and egt were lower. $10 says mine will look the same when I open it up.
Sweet!
Side note- just tore my motor apart last night out of my dually and the #2 main has 2 distinct gouges in the bearing face and the bearing itself has some chipping of the bearing face material. Looks like the gouges are from burring on the outer edges o the oiling passages. My motor has crowers and SoCal cut and coated .020's. Has aprrox. 6-7k on motor. And I pulled it because #1 rear housing adapter had a bolt stripped out in the upper oil pan and oil leak around the adapter itself and #2 I was wanting to do cam, heads, main studs....etc. anyways so I went on ahead and pulled it. Wanted to check the #2 main bearing for signs of wear and I believe I may have saved myself a crank failure. Gonna have the crank mag checked for cracks to see if I can spot an early failure area. I'll post my findings when I get the crank mag'd.
Broken crank
2007.5 LMM 210,000km... Broken Crank. Was pulling my trailer at speed limit when truck died. The guy that opened it up tells me it has stress cracks that look like it's been ready to go for awhile. He also tells me that 7 out of the 10 Duramax's he gets for rebuild are due to a broken crank, some tuned some totally stock. Apparently there is a casting issue that GM won't admit to.... There goes 70 grand down the drain. Thanks GM, Im a 7.3 Powerstroke man now!
2007.5 LMM 210,000km... Broken Crank. Was pulling my trailer at speed limit when truck died. The guy that opened it up tells me it has stress cracks that look like it's been ready to go for awhile. He also tells me that 7 out of the 10 Duramax's he gets for rebuild are due to a broken crank, some tuned some totally stock. Apparently there is a casting issue that GM won't admit to.... There goes 70 grand down the drain. Thanks GM, Im a 7.3 Powerstroke man now!
I've worked at a GM dealer for about 8 years now. Our diesel techs and shop foreman have never seen a broken crank. We work on alot of them too, including medium duty trucks. They thought I was crazy when I asked them after I bought my truck lol. They had never heard anything like it.
Maybe he's the only guy there that works on them. There is not that high of a breakage rate on DMax cranks. I would imagine that percentage wise other brands have similar problems.
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Before everyone broke a crank;
How many burnouts/high revs to complete stops were made?
Who revs their engine up and down and let's off quickly?
How did you drive your truck before? Cool or like a race truck? I feel revving the engine at high rpm and then letting off abruptly definitely places a factor. These cranks seem to not like abrupt high rpm to a sudden idle. I feel stock or race, the cranks are beaten up with incorrect driving. I'm sure most will beat on the engine and not drive it smoothly; the whole time. So if that's the case, may as well buy a billet crank. I've also been told by top engine builders that billet mains have a problem with oiling.
But what do I know; just my 2 cents; out of tens of thousands.
How many burnouts/high revs to complete stops were made?
Who revs their engine up and down and let's off quickly?
How did you drive your truck before? Cool or like a race truck? I feel revving the engine at high rpm and then letting off abruptly definitely places a factor. These cranks seem to not like abrupt high rpm to a sudden idle. I feel stock or race, the cranks are beaten up with incorrect driving. I'm sure most will beat on the engine and not drive it smoothly; the whole time. So if that's the case, may as well buy a billet crank. I've also been told by top engine builders that billet mains have a problem with oiling.
But what do I know; just my 2 cents; out of tens of thousands.
Why do you "feel" revving the engine has anything to do with it? I'm not sure why letting off and returning to idle would play a art in anything particular.
The mark is into the radius and lines up with the initiation point.
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Sent on the run from my Cell Phone
Revving it up and down like an idiot
Real racers dont rev up and down "abruptly"
it's best to bring the engine up to a speed and and ease off slowly
i see many guys revving thier engines like they own a street bike
doing burnouts at 4k then letting off only to let the engine stop doesnt help