Since there's more LBZ/LMM's broke in the poll, does 6th gear have a lot to do with it? I ran 6th in my truck for 5k miles until i went to 35's, like the lug but too scared to run it.
Broken Crankshaft Count?
- Thread starter EDP
- Start date
I used to cringe a little when i lugged my truck hard on my big tune. Ive since then made some tcm changes so it will downshift without lugging the shit out of it. Still holding together:thumb:
I think if it had to do with torque, the crankshafts would be breaking toward the rear where most of the torque is applied. They are breaking near the front pointing more at a harmonics problem.
I worded that wrong, I don't mean it'll lug, it downshifts too easy imo, but I just meant the lower rpm's while cruising. Seems like that's the sweet spot for em to go.
I gotcha. So youre saying that with the 6 speeds they may be at a rpm thats more likely to break the cranks due to harmonics bc they run slightly lower rpm down the road. I guess that it would depend on how fast you consistently drive bc a 5 spd if driven at a slower speed would be at the same rpm as a 6spd.
At 70 in 5th I'm at 1950 rpm, at 80 I'm at 2200, I usually run between 75-85 mph. Not ran 6th enough to remember but the rpm at 90 is lower than 75 in 5th.
75 mph in 6th you're at ~1800 rpm. According to Fingers research, that is the rpm range that gives the most harmonic movement on the front of the crank. I have my tcm tuned to not shift into 6th until 77mph and it downshifts quickly to avoid lugging under 2k rpm.
I'm at close to 1600 in 6th at 70, I think it's a little less. And mine downshifts quickly as well, but doesn't hold the gear, it up shifts and downshifts repeatedly, it's annoying so I don't even run 6th, unless I'm close to 90mph.
LML's have a more sophisticated injector/cylinder balancing system than the others do. I'd attribute it to that more than anything.
Yeah, I've read they have some timing and fueling adjustments built in for this, don't k ow for sure, but if so it seems to help.
But you can't tell me the guys tuning these trucks have a way of controlling either said algorithm or multiple tables that have the available calculations. There also isn't any actual printed facts that this is so. Just speculation that there is more to the injection system. It's also not said that that's what the assumed injection system is helping to fix. Friend of mine (josh Chaves) has broken open these lml ECMs, built his own tables and done ALOT of work on them both tuning and finding "hidden tables" in the hex coding and I've not heard anything from him about this.
Remember, most of the trucks in this thread are NOT stock. A very small percentage are stock. A majority of the lmls here are tuned. If the ECM did have this setup to adjust injection to lessen harmonics, tuning would screw with it. It would have to work like a limiter if it was used in 6th gear, under load, lugging the engine which isn't the case. How else you going to lessen harmonics? Some sort of pilot injection? It would need another table. Pull or add timing per cyl? Another table needed and you created a limiter. Same would go for fuel.
So in my opinion, I don't buy it.
Diagnosed another lmm with a broken crank today. Won't get to disassemble it and don't know any history on it. Auction truck. 163k miles, balancer all over the place and bangs like hell.
I know it's a fluke thing but I hate it. Every time I see one makes me want to put my truck up for sale and buy something else.
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I know it's a fluke thing but I hate it. Every time I see one makes me want to put my truck up for sale and buy something else.
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And you would get on a forum about something else and discover how trouble free the Duramax you traded in really was.:roflmao:
X2 ^^ doesn't matter what you buy, They all Break. I find it ironic all the people bitching about broken cranks on a performance forum
If you want longevity Leave it stock :hug:
X2 ^^ doesn't matter what you buy, They all Break. I find it ironic all the people bitching about broken cranks on a performance forum
Problem is stock is breaking them too.
If it has tires or tits you're going to have problems with it
Fixed it ....:thumb:
While I agree, when you look at the numbers statistically the odds of breaking a crank stock are pretty slim IMO.. There are well over a million Duramax motors produced and on this board (Performance forum) only a 100 or so (mostly tuned) have reported a broken crank. Obviously there are a lot more breaking then we are hearing about but overall I think the chances of breaking a crank on a stock motor are pretty slim.. :beer