C15 Vibration

Electronics these days can do some crazy things these days I can not explain. One example is a 60 series Detroit I would have bet a paycheck it was going to through a rod. Then the operator said when it starts doing that going down the road I can turn the key off, it stops knocking, and in about 15 seconds turn it on and it runs fine. It was a bad ECM.
Normally a mechanical vibration like that is caused by: A bent connecting rod. Different weight pistons. Displaced springs in the pressure plate. Shoulders on pressure plate bolts are to long and bottom on flywheel before pressure plate is pulled tight type problems.
Engine to flywheel housing dowel pins are factory installed to align that housing with the crank on that engine. As long as they stay together it can be removed and just slapped back on. Alignment is correct. When the block or housing is replaced the field fix is remove the pins or drill the housing holes out a little. Then use a dial indicator and center the housing and crank with in .008 inch. Misalignment normally causes clutch problems not severe engine vibrations.
Looking at your history I see you joined when you made your first post on Sept. 27 about the same problem. Then you mentioned it went away after the head was replaced. That should remove the concerns about mechanical problems. What else would cause that and not through codes? A mechanical problem with an injector? Were they replaced? A bad cam sensor and or wiring to it?
Others here know much more about these engines than I. I have found that if I thank people who have helped me or anytime I learn something they are more likely to help me in the future. Never respond with a bad attitude. Welcome aboard and good luck.

 

Just some thoughts based on your description of the issue. Inspect all engine and transmission isolators and mounts very closely for wear. Look for anything from the engine or trans hard contacting the frame or the cab itself. Have an overall health status performed on the engine. Cold start and perform cylinder cutout to be sure all cylinders can run on its own all the way up to operating temp. Any week ones need addressed. Overhead set? The type of problem you are chasing is the toughest to track down, good luck....

 

Unfortunately this sounds like a broken crankshaft. It is a fairly common Cat issue. Drop oil pan and main/rod caps as needed to inspect. Concentrate on #5/#6 as these were the popular journals for cracking.

 

Ok, so you've covered most of the bases I've mentioned. Judging by the length of time you say the issue has been occurring, I'm going to rule out a broken crankshaft. This usually makes a heck of a lower end racket that would make you scared like a little girl to even hook a trailer up much less haul a load with it.

You start talking about having the head off and rocker buttons failing off makes me curious of the overall health of the engine. Was this engine in-framed? If not how many hours/miles are on the engine? Me thinks this will likely come down to being a fueling imbalance between injectors. Enough of a difference in fuel between cylinders to cause a shake but not a dead hole. I've felt it a thousand times and each time they are all different, even after complete overhaul some just come out smoother that others. I know your hoping for a silver bullet, but you may chase this for a while. If it builds good power and pulls, I say run it. But you can feel it, not me.

I also don't think this issue caused your clutch to break. I see the disc dampening springs broken all the time on perfect running and different engines and this IMO is not the cause.

 

Thompson Cat in Dothan, AL has a pretty good Acert mechanic there. They are the only ones besides myself that I’d let touch my motor.

 

with your motor in the million mile club. have you had your "crankshaft dampner" or harmonic balancer inspected or replaced.
it has a nasty way of throwing weight around.
as well as the bull gear. both should be checked.