Growling noise between 600 and 1000 rpm

bmoore2156 · 07-19-2008, 09:20 AM

I have the ppe race and 4'' tb exaust and shortly after I installed it I started hearing a growling noise that comes and goes. It usually happens when I let off the gas the the rpms are dropping through 600 to 1000 range. Every once in a while it will do it when it is at an idle (not moving). It almost sounds like a tire rubbing noise that happens when I am at full wheel lock with my 285's. Does anyone have any ideas? I am running the ppe on level 3. I have about 12,000 miles on the truck.

Clevelands_Duramax · 07-19-2008, 01:22 PM

i installed mbrp stacks on my LMM and have PPE also.. When you put turbo back systems on the LMM, with the type of turbo it uses i hear that this is normal, something about the turbo vanes and what not.. someone the other day told me something with a wastegate but mine does this too..

**daddysLBZ** · 07-19-2008, 05:21 PM

Mine has done it since I had it..Don't know what the hell it is either,all is intact also,so it is not something I lose sleep over,but damn,,it sure makes me wonder,I have the ''groan'' when I slow and turn..

It is really not been a problem,so I don't worry too much...Enjoy ya truck!!!!!!!

**daddysLBZ** · 07-19-2008, 05:26 PM

Quote:

Originally Posted by Clevelands_Duramax

i installed mbrp stacks on my LMM and have PPE also.. When you put turbo back systems on the LMM, with the type of turbo it uses i hear that this is normal, something about the turbo vanes and what not.. someone the other day told me something with a wastegate but mine does this too..

Would you say it groans like this because the vacuum is low at idle??That is the only explanation I can see,,so when slowing and turning,I would say it is normal.P.S. my LBZ does it too,

also a guy or two on here with LLY's and LMM's have heard the sound.I think all is well for now..It would be nice to know what causes the condition though!!

Clevelands_Duramax · 07-19-2008, 07:14 PM

What it is is the turbo vane is switching, there is nothing to worry about this is a normal thing. I think it sounds cool and when your at a lite and you have al the windows down and all the sudden the people next to me are checking out my stacks then all the sudden you here this really deep rumble.. lol i only wonder what goes through there mind.

**Tow Master** · 07-19-2008, 10:41 PM

I think what your describing is the exhaust rattling off the transmisson crossmember. Mine did it when I first installed the exhaust. I basically used a floor jack and a block of wood to bend one of the exhaust mounts near the front of the bed up.

I have pics at work. If you dont figure it out I'll post them on monday!

Clevelands_Duramax · 07-20-2008, 05:09 AM

No, this is not a rattling if you start your truck and u let it idle... you hear the normal hissing sound coming out the exhaust, then all the sudden the hissing sound goes away and there is a really deep low rumble... like it turns into a muscle truck, that is one of the vanes changing in the turbo, its a reallly cool sound.

bmoore2156 · 07-20-2008, 08:32 AM

Quote:

Originally Posted by Clevelands_Duramax

i installed mbrp stacks on my LMM and have PPE also.. When you put turbo back systems on the LMM, with the type of turbo it uses i hear that this is normal, something about the turbo vanes and what not.. someone the other day told me something with a wastegate but mine does this too..

When I bought the truck I think the salesman told me it doesn't have a wastegate, I am not sure if this is true or not.
The only resaon I ask about this noise is because it seems to be getting worse and I didnt notice it right after I installed the PPE and 4''. I think it was almost 2 weeks after the install I noticed the noise. It also seems to do it at an idle more on a hot day then a cold day but always seems to do it when letting off the gas right when it hits 900 rpm.
When the truck is idleing in park and it decides to growl, (somewhat rare) you can feel the vibration in the gas pedal.
I wish I could record the sound for you guys... hmmm, maybe if I cant figure it out I will make a youtube video and post it. anyway. thanx for all the replies.

**Landscapeman** · 07-20-2008, 08:54 AM

I have the same noise.

**Landscapeman** · 07-20-2008, 08:56 AM

As far as I know there is no waste gate on the LMM's. I have seen this noise on the variable g. turbos. I have heard many ideas but never a definite answer.