BuffaloSS

iTrader: (3)

For the past month, I've noticed a rattle/chatter from beneath (?) the car when I'm cruising down the street and the engine switches from 8cyl to 4cyl mode. Something is rattling. It stops as soon as it gets back into 8cyl. I mean it IMMEDIATELY stops when this happens.

Now, IDK if it's the speed that determines the switch back to 8 when the car is slowing to a stop, or if the gear the tranny is in does it, but it usually happens after it's in 4...and never when accelerating in 8cyl mode.

Could there be something in the engine rattling ONLY in 4cyl mode, or something in the tranny that is rattling? Could the different engine cycle in 4cyl cause something within the exhaust to rattle like that?

Unfortunately, it seems like something that the dealer isn't going to figure out easily, but I'm trying to figure out what I can point them towards during their initial investigation.

Kazmaniac

IMO 4 and 8 cyl operation change the harmonics in the vehicle. I've always felt I had a vibration off the right side of my exhaust, both the M/F and stock. My Z had a heat shield that was loose one time causing a rattle.

Dang Chris ... feel sorry for you on this car man. I would have sold it long ago, just doesn't seem to end.

Saw this last night - don't know if I want a 4-door though:

06WHITEMCSS

I could drive that!

BuffaloSS

iTrader: (3)

That car just doesn't do it for me. It's ugly from the front and rear. The front looks like every other pontiac, including the torrent and vibe, and the rear is just ugly all on its own. The only reason people are creaming over it is b/c it's 360hp and RWD.

Tap Dat SS

If still under warranty take it to the dealer. There is a TSB on a bellhousing cover that will make a rattle normally from 45-55 and in 4cyl mode.

BuffaloSS

iTrader: (3)

Thanks for the info. Got a TSB number on that? I might take the wheels off this weekend and take it back to the dealer.

pgbSS

My car does this, but only when slowing to a stop. I don't hear it with the windows up, but with the windows rolled down it almost sounds like marbles in the engine. I only hear it when slowing to a stop before it goes back to V8 mode maybe 5-10mph. I first thought the Diablo program screwed something up, so I reset to factory tune and it still does it. It doesn't do it now because I'm running the nonDOD tune since my mileage isn't any better having DOD working.

Count of Monte Carlo

Wow I hear the same thing on my car as well...Bellhousing cover....Like the the plasitc cover that blocks off the Torque converter inspection???

Feel the same for the G8 as well Mr.Buffalo, Pontiacs used to look like '77 T/A's now they all look like different reditions of a GrandAm from '89....

Kazmaniac

Ahhh, the front end is what grabs me ... I guess I'm drawn to the more aggressive styling. Chevy's are getting more and more vanilla bland for my taste. Agree on the rear, the valiance / splitter looks real cool, but typical GM's lack of inspiration on taillamps. Never understood the chrome brake lights.

I like the pic Emerson posted of the 2-door.

BuffaloSS

iTrader: (3)

OK, so I'm not alone on this. pgbSS, that's EXACTLY what it sounds like (marbles in engine). Still would like a TSB number if someone can get it for me.

I agree...kaz. Chevy has lost a step or four on the competition...I'll give you that.

Count of Monte Carlo

Ok I changed the oil and the noise gradually went away. 6K on Mobil 1 Regular 5-30 Synthetic and a Purolator Pure One Filter. I'll be changing the oil at 4K and ignore the monitor. Apparently these DOD lifters are too sensative. 21% on the monitor. I did notice the pan was alittle wet on the trans side....Seems like a VERY light coating of oil, not dripping at all. I might pull the TC inspection cover and examine further...

Tap Dat SS

OK I've been looking for the TSB on this noise concern and I couldn't find one. My memory was inaccurate on both counts actually. I talked to the tech who has done a few LS4 cars for this concern and he said the fix has been repostioning the trans. dipstick tube. At a certain RPM and in 4cyl. mode there is a reverberation that makes this noise (I did hear it in one of the cars we did) and it does sound as you explain it.

Count of Monte Carlo

My trans dipstick tube was hitting the STB and causing a rattle for me, so loud I though it was comming from the dash board.

Like I said I changed the oil and the sound went away.

BuffaloSS

iTrader: (3)

I'm getting close to the 6k on M1 oil & filter (OLM showing ~15%), so I'll change that this weekend and see what happens. However, the noise is getting louder and more frequent, maybe due to wear and/or ambient temp (plus windows are down more often now).

Just this AM I was regretting getting rid of the Diablo tuner, which I used to disable DoD amongst other things, then I remembered that I could do the same by switching to 3rd gear instead of Drive. I did that and the rattling stopped IMMEDIATELY. It's definitely related to DoD.

I'm wondering if I should just take it in before I change the oil to make sure it gets addressed before the warranty expires. Lifters/oil related or not, this is not normal, nor should it happen at 34,000mi. I'll add that to my problematic transmission and let them figure them both out at the same time.

Count of Monte Carlo

I'd change it, if you got a chance to not let those monkeys into the engine I'd take it...my buddy has been recommending Pennzoil Synth and Castrol Syntec, apperantly they changed their formula, seems to work well on the LS engines and thier lifters....Unfortunatly I put in more mobil one, the sound comes and goes now so its definately oil related....I'm not going to push the oil changes that far anymore....4K is the limit. Too much dirt in the oil...


My passenger side outer axle boot is leaking......

BuffaloSS

iTrader: (3)

I miscalc'd the oil change interval. I'm at just 4400mi and 15% remaining.

I made it a point to drive around in 3rd today and when I tried to hear the sound again, I couldn't make it happen again. I hear ya on the "don't let them start tinkering" issue, but I'm no grease monkey myself, so I can't afford to have to mess with it myself at 38,000 if it gets worse over the summer.

Sint3k

I turned my exhaust off to the quite flowmasters and i started to hear noises that i didn't hear when the car was new. I quickly reached down and turned the exhaust cutout back on no more weird noises :-\

pgbSS

Well, I gotta admit when I read that dipstick solution I thought wtf that aint gonna work. I had my DOD tune in and that rattling came back. I took out the tranny stick and repositioned the tube some (gave it a yank to the drivers side). While I was under the hood I checked the oil. Later when I took the car out again, no noise. I don't know if one of the dipsticks were loose in the tube or if moving the tranny tube did it, but no more rattles. Thanks for the tip tap dat SS.

BuffaloSS

iTrader: (3)

Well, it's not the oil. I just changed the oil and filter yesterday and it's still doing it. I forgot about the dipstick issue, but I'll try that next.

Count of Monte Carlo

I changed the oil twice. Pulled the mobil 1 and filter and filled with pennzoil synth and a purolator pure one(new design gold)... Its quieter....I dont think its going to go away completely...It might've been somthing that this engine does but i didnt know till it was so loud....

My poor axle.....Should be getting fixed tommorow.