LLY: Intermittent vibration at idle?

[Devon]

Ok, I know there has been a few topics like this before, but I would like to know why a lot of lly's have a motor shake at idle. It will go smooth for a few seconds then shake a faint bit and so on. Done this ever since I have had the truck, rail pressure is normal and doesn't jump at at all. Does anyone know for sure why this does this? My 06 Lly never had a intermittent vibration at idle. I see a lot of other people that have this issue as well. All with 04.5-05 lly's.


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[Trotorx2]

My LBZ has a vibration at idle that kind of goes in waves...it vibrates for a couple of secs...goes away for a sec then starts again. Sounds a lot like what you are describing.

 

[blk smoke lb7]

Same here my lb7 does it at start up, but after warm it seams to go away

 

[Devon]

Yeah I mean once it's warm it's there still but not bad at all. I wonder if it's just normal?


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[DuramaxPowered]

My LMM has done this since it was new. I have 92k miles on it without problems. I loaded a 500+RWHP tune at 2K miles, compound turbos at 26K.

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[07keo02]

I had this problem for a while too with my lb7. I found my crank pin was bent so I fixed that but to my surprise it still had a slight shake at idle. One thing I was always curious about that could cause a slight imbalance at idle is the fact the drivers side manifold is so restricted compared to the passenger side. I have read some people's truck idled smoother after doing a full bore manifold. I know it's a long shot to be the problem but just a thought.

 

[07keo02]

I should add that I think the stock mounts (atleast mine) allow a lot of travel. I upgraded to the MA mounts and now it's more of a slight buzz than a shake. I was concerned of vibrations after the MA mounts because they're more solid but actually made it smoother for me. If I had the money right now I would try an LML manifold as I'm very curious to see if it would smooth out the idle at all.

 

[GeneralTJI]

I thought the TC can cause a vibration at idle too. I know triple discs are more prone to this, but my DPC single created a slight vibration that cycles at idle...

 

[blk smoke lb7]

I have rdl manifolds and uppipes so i dont believe thats going to make a differance as mine is still doing it

 

[07keo02]

I have rdl manifolds and uppipes so i dont believe thats going to make a differance as mine is still doing it

Yeah I figured it wouldn't be that easy I had just read a review where a guy said his truck idled smoother after a full bore manifold so it was a thought. I thought it might of been from my single mass flywheel but it's obviously happening in allison trucks too. The only other thing I had read was a bad belt tensioner can cause a shake as well but mine was replaced and its bearing was shot and I saw no difference.

 

[arneson]

Vibrations from what or where are u noticing it? I cant say i have ever had a vibration. Idles smooth and doesnt change. Im super picky and pick up on noises easy. I hate them. But im kinda lost on this one being there are so many of u guys having this issue. I have triple disc, twins, ect and dont notice a thing?

 

[07keo02]

Vibrations from what or where are u noticing it? I cant say i have ever had a vibration. Idles smooth and doesnt change. Im super picky and pick up on noises easy. I hate them. But im kinda lost on this one being there are so many of u guys having this issue. I have triple disc, twins, ect and dont notice a thing?

Mine was more of a slight shake, like something out of balance. Could see the engine move side to side at an idle and my shifter (zf-6) was wobbling back and forth more than usual. Still did this with a new balancer/pin, new injectors and new fpr. What fixed it for me was the ma mounts. Obviously they didnt fix an unbalance but are more solid than stock and dont allow the engine to move much and in turn the shifter stays put.