Is This True about the crankshafts?
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Well I guess it doesn’t hurt to check all the wiring to the injectors.
. Yea you got that right. It’s crazy to see some trucks blow up with so low mileage that’s what gets me.
It is not the wiring harness. It is not an injector sticking open. On the surface it's a good theory but it doesn't pass muster. Almost universally a rod will fail before a crank shaft. If there was any significant merit to the theory, we would see bent or snapped rods in combination with crank failures. We don't.
If the engine is running and the injector locks open, the injector will never inject enough fuel to hydrolock that cylinder. If it injected enough fuel to actually hydrolock the cylinder it would leave a massive black cloud behind the truck and the injection pressure would be significantly reduced for all the other cylinders.
Generally speaking a hydrolocked cylinder only occurs on an engine that isn't running (see radial engines).
My current theory is that it's the transmission snapping cranks. It's the only other component strong enough to snap the crank. It seems the aisin, with some drivers, including myself, can be overly aggressive in its shift strategy. It can change gears so hard at times it felt like I got rear ended. Our Aisin is basically the transmission from an engine that did 800 ft.lbs rated, which in the calibration is probably closer to 1000.ft.lbs. The calibration includes a calculated offset for parasitic losses. So when our little v8 is putting out its peak torque and the transmission decides it's going to make a fully locked, nearly instant gear change, I think that's when the crank snaps. The Aisin has a reputation for violent shifts in our truck and the rams for people who tend to drive the truck lightly. I baby mine and before my tune the transmission was a complete bear.
Don't get me wrong, a frozen injector needs to be addressed but it doesn't pass the test when you start digging deeper into what it takes to snap a crankshaft.
If the engine is running and the injector locks open, the injector will never inject enough fuel to hydrolock that cylinder. If it injected enough fuel to actually hydrolock the cylinder it would leave a massive black cloud behind the truck and the injection pressure would be significantly reduced for all the other cylinders.
Generally speaking a hydrolocked cylinder only occurs on an engine that isn't running (see radial engines).
My current theory is that it's the transmission snapping cranks. It's the only other component strong enough to snap the crank. It seems the aisin, with some drivers, including myself, can be overly aggressive in its shift strategy. It can change gears so hard at times it felt like I got rear ended. Our Aisin is basically the transmission from an engine that did 800 ft.lbs rated, which in the calibration is probably closer to 1000.ft.lbs. The calibration includes a calculated offset for parasitic losses. So when our little v8 is putting out its peak torque and the transmission decides it's going to make a fully locked, nearly instant gear change, I think that's when the crank snaps. The Aisin has a reputation for violent shifts in our truck and the rams for people who tend to drive the truck lightly. I baby mine and before my tune the transmission was a complete bear.
Don't get me wrong, a frozen injector needs to be addressed but it doesn't pass the test when you start digging deeper into what it takes to snap a crankshaft.
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Could that transmission oil thermostat help it? Shift any better or is it just a waste of money?
I don’t have a good answer to that. I’ve never had an issue with mine not wanting to lock at lower transmission temperatures. Mine will lock up with an engine temp of 140F.
The only time mine has ever flared is when I was flailing about trying to correct bad decision making on my part.
My transmission is so much different with my tune now that I now only have vague memories of how uncivilized it was.
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Yes, the trans thermostat is awesome.
I’ve had mine about 5 years. It cured the shift flare and makes the shifts so good. That, coupled with proper maintenance, will make for a great riding truck.
Additionally, I was told by my Nissan Cummins tech that the transmission ‘learning’ procedure doesn’t happen unless the trans is between certain operating temps. I hope @realbored can confirm this- he’s our resident Nissan tech. If you monitor with Ezlynk or any other device, you’ll notice that the cooling of the trans is almost TOO good. Mine used to stay too cold, IMO.
Bottom line, it’s worth it. It allows the trans to actually adapt to your tuning and your driving style. Highly recommend.
I’ve had mine about 5 years. It cured the shift flare and makes the shifts so good. That, coupled with proper maintenance, will make for a great riding truck.
Additionally, I was told by my Nissan Cummins tech that the transmission ‘learning’ procedure doesn’t happen unless the trans is between certain operating temps. I hope @realbored can confirm this- he’s our resident Nissan tech. If you monitor with Ezlynk or any other device, you’ll notice that the cooling of the trans is almost TOO good. Mine used to stay too cold, IMO.
Bottom line, it’s worth it. It allows the trans to actually adapt to your tuning and your driving style. Highly recommend.
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Great explanation about the
thanks for clearing this up. I agree with your assessment/explanation of the crank failure. I try not to abuse my truck. So far 45K with no issues. Deleted along with EGR delete. Also have oversized intercool. Pull a 8000# TT and the transmission acts better with a load on it. Cruise at 70mph no problems. The truck runs great. Love it.
Yes it needs to reach a specific temperature before it goes into a self learn mode. I can't remember the exact temperature off the top of my head but I believe it is in the 170F range.
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Has Nissan issued any tcm updates that someone could be missing? I know my truck has had several reprograms at the dealer but I’ve never seen the specifics before.
I wanted to specifically address the crankshaft bluing. It is a heat treatment process. It takes 200 to 300 degrees C (450-575F) to turn the crank blue, depending on the exact formulation of the crank. I run delvac 1 5w40 in my truck, the msds says it has a flash point of 233C.
There does not appear to be any supporting evidence that these temperatures are occurring within the engine.
In the video, look at the sheer, it’s a nearly perfect sheer at a right angle to the throw of the crankshaft. How it would break if the crankshaft were over loaded.
There does not appear to be any supporting evidence that these temperatures are occurring within the engine.
In the video, look at the sheer, it’s a nearly perfect sheer at a right angle to the throw of the crankshaft. How it would break if the crankshaft were over loaded.
Indeed. I posted this in another thread, but here is a picture of the production line at the factory and will post again here. Look at the visible crank counterweights...same violet/blue on the new part. The guy at CFT puts a lot of stuff out there in his videos...some helpful. Some not so much...
![Automotive tire Motor vehicle Automotive design Engineering Gas]()
There have been TCM updates released for various issues ranging from shift complaints to lack of power depending on model years and current TCM/ECM software programs.
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I wonder if that’s what caused the decrease in destroyed cranks. I’ve never seen any proof that cummins switched up the cranks during the first year or two. From personal experience, the trans in my 16 was super rough shifting when it was new but has mellowed out over the years.
There was a part number supersession beginning in trucks built in 06-2017.
Right. The part number changed then. A couple--maybe 3 years ago pre-Covid and price increases--you could buy the old crank on NIssanPartsDeal for like 398 bucks. That part number is now long unavailable and replaced by the new one. The early ones were made by a supplier in Germany. Normally a place that has high quality metallurgy. I guess we'll never know what the suspected problem was--or if that was even the real problem. Bad batch, poor quality/grinding/finishing practices? At the same time, a number of cranks with the new part number have broken and many 2016's have gone way over 100,000 miles. Who knows really....
The January 2016 engine I have with the broken cam has the same supplier as this early 2016.
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Thanks for all this great feedback and information. It comes down to good maintenance, don't abuse the truck and oil analysis history which really keeps a watch of what's happening internally. I really believe in oil analysis.
Example of the report from my 2017:
Most metals are lower than last time, which is what we hope to find after using a shorter oil change interval. Copper went up a little and it shows a little extra brass/bronze wear. It's barely in the highlight range (twice average), so we'll just see how it trends from here. There's no evidence of coolant contamination, and the 440ºF flashpoint shows no measurable fuel dilution. The viscosity is slightly thin for 15W/40-grade oil - maybe because some of the thinner oil from last time carried over. Low insolubles show excellent oil filtration. Check back in 7K-8K miles again.
Example of the report from my 2017:
Most metals are lower than last time, which is what we hope to find after using a shorter oil change interval. Copper went up a little and it shows a little extra brass/bronze wear. It's barely in the highlight range (twice average), so we'll just see how it trends from here. There's no evidence of coolant contamination, and the 440ºF flashpoint shows no measurable fuel dilution. The viscosity is slightly thin for 15W/40-grade oil - maybe because some of the thinner oil from last time carried over. Low insolubles show excellent oil filtration. Check back in 7K-8K miles again.
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I’m no expert on crankshaft failure by any means, but I wonder if anyone has considered the harmonic balancer as a potential culprit (in conjunction with the transmission shifting issue. As I recall, the GM 6.5 turbo diesel had a note in the service manual for routine inspection of the rubber in the harmonic balancer as degradation would lead to crankshaft failure. Just a thought...
Was my initial theory, but overall evidence isn’t as strong for that theory.
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