Need help with a 2015 Freightliner dd15 harmonic vibration

Ok, just did that, it changed the modulation of the vibration higher while maintaining 65mph. I dropped to 9th gear and rpm's were at 1800 and I was on pretty flat roads using very little power to maintain the speed.

 

Yes you can feel it in the seats.

 

Sounds like its engine/transmission related then if that's the case.

 

You can rule out drive shafts and rears then. I'd say it's in the trans or engine. Does the engine feel or sound as if there is a miss to it?

 

LOL. Yes I agree, I have been trying to tell Freightliner that, but they keep saying it's because of the super singles even after they put duels on and it still did it.

 

YES!!!! If this was a gas powered vehicle I would say a bad spark plug or the timing was off when the HP/tourqe are at a certain point. But it's a deisel engine, so that doesn't really apply.

 

Injectors are what I would be looking at then.

 

I would start with the basics. Make sure all your engine mounts are tight, engine is mounted solid to the transmission (ie bellhousing bolts aren't loose), pop off the inspection cover and check for missing or broken parts. Really anything that could be related to engine mounting or engine balance.

 

Now I just noticed you said something about a miss. Yes I would consider injectors as well in that case.

 

It might not be an injector, could also be a wire or wire harness issue. Had a friend that had an 09/10 Cascadia, and had troubles with broken wires or corrosion in the engine harness. FL dealer that found it said it was a fairly common problem with them. I don't remember what symptoms his truck had though.