Bad shaking/ vibration starting at 1300 rpm

[MadMax17]

I'm hoping someone has had this same issue and can share what they have found, my truck is shaking badly starting at 1300 rpm and doesn't stop until around 1800 rpm. It doesn't matter if the truck is in gear or in park/neutral, the shake is still there (worse under load). I tune the truck myself with efi live but also have tunes from Duramax tuner and Idaho Rob that all do the same thing.
I pulled the inspection cover off of the trans bellhousing earlier and inspected the flexplate - I did not see any evidence of cracks or damage but at the moment I dont have anyone here to bar the engine over while I look. balance rates are all within spec in neutral and in drive, the readings are below. The weird thing is it feels like a misfire when it happens, I used the EFI LIVE scan tool earlier to cut each injector individually and see if there was little or no change with one. I felt a noticeable change when cutting each injector at idle, but when i raised idle to 1350 and cut cylinders the shaking actually smoothed out a little when i cut #6. I tried this several times with every injector and had the same results every time.
I've looked into several threads on this issue today and plan on checking the harmonic balancer and having someone bar the engine over while i look at the flexplate better this weekend. There is no noise associated with the shaking, only the vibration.
Any insight you can give is much appreciated.


These are the balance rates off my v2 read at idle in park:
1:1.8
2:1.1
3:0.9
4:-3.0
5:0.0
6:-1.4
7:1.5
8:-0.9

 

[S Phinney]

Pull your belt off and see if you can move the balancer up and down by hand. You could have a broken crank issue. Hopefully you do not. Good luck with it.

 

[Awenta]

That was my thought. Hope not though.

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[MadMax17]

I'll check that when I get time this weekend, I feel like if it was a broken crank there would be noise associated with it as well as shake through the whole rpm range or at least at idle for sure. I'll update as i check/ find things. Thank you for the replies.

 

[Awenta]

Not always. You can sometimes just look at the balancer with the motor running

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[JoshH]

You might check and make sure the balancer hasn't broken the crank pin and spun on the snout.

 

[MadMax17]

I'm going to pull it off this weekend and see. I'm hoping its something that simple, I really doubt the crank is broken, running a pretty conservative tune right now.

 

[Awenta]

Watch it running first.

Theyve broken on 100% stock trucks.

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[MadMax17]

The crank is fine, checked all converter bolts, all are tight. Removed balancer and pin is still intact no signs of damage, ran engine without belt still had same result. It is starting to have a small miss at idle when cold in the morning but when I cut injectors all are contributing enough to make the vibration change and have a noticeable knock noise when cut. Checked flexplate for cracks and don't see any damage. Cly #1 balance rates have been higher the last 2 days, up to 7.2 this morning after checking all these things. Thinking about pulling valve covers to verify clearance and swap injectors to different cylinders to see if rates follow. If they don't next step will be a compression test.
If anyone has had this issue please share what you have found, my time is limited due to work hours but this issue is driving me crazy.

 

[Awenta]

What is desired vs actual frp?

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[MadMax17]

Fuel rail pressure stays very close to desired at all times except full throttle on my hot tune.

 

[MadMax17]

Well I looked into it more yesterday and checked the motor mounts again, found the drivers side glue had come loose, removed it just now and put a bolt through the mount and reinstalled it, shake is just as bad with the mount fixed, the passenger side looks to be in tact so i will tackle that one another day.
I'm going to pull the converter bolts a minute and check to see if its in the trans, I'm running out of ideas at this point, if anyone has any suggestions please don't hesitate to post, this is driving me crazy and being that its been 110* outside, I really don't like working on it after wrenching at work all day. Thank you again for the replies.

 

[dirtydmax]

Have you ran it with the belt off?I pull mine and it's smooth as glass but with it on is a different story.bad vibrations!

 

[MadMax17]

So far i have:
Run the engine without the belt
Removed the balancer and checked the pin
Fixed the broken drivers side engine mount
Checked crank endplay
Checked all converter bolts for tightness
Flashed the 100% stock tune in to verify its not in tuning
Checked exhaust system to see if its contacting anywhere
Checked injector balance rates
Cut cylinders using scan tool - all injectors contribute close to even

I will probably buy a diesel compression tester tomorrow and check that, it just seems like its in the trans to me so if I don't find any compression issues I'm going to at least pull the converter bolts and push it back so I can determine if its in the engine or trans. I was going to do this tonight but don't have the patients for it right now.
Please keep the thoughts coming, I've read every thread I can find on this issue and seem to have eliminated all of the common problems people find.

 

[NC-smokinlmm]

You pop off the oil fill cap while its running to see if you blew a hole in a piston yet?

 

[MadMax17]

Yeah Blow by is not excessive, earlier after doing the motor mount I hadn't driven it. Just drove it to the store and it is night and day difference when in drive. On the way home from work today I was nervous to even be driving it the shake was so bad. Now it is hardly noticeable while driving. The shake is still present in park but seems to be a little better after swapping to stock tune and doing a full flash of my dsp tunes. I'm still going to look into the shaking and will update if I find anything but its not as much of a concern now.