LS1vazquez

Hello.

About two days ago, we finally got the GMMG catback system bolted up to the stock exhaust. We jacked up the rear end of the car, and used a Sawsall to cut out the old exhaust.

We used all the provided clamps and bolts, and we didn't jimmy rig anything. The system was a perfect fit. When we fired it up, it was 100% better then the stock GM catback.

Well, now I have put some miles on the car, and the system now has a rattle to it when I engage the clutch from an idle. During driving, and WOT, the system sounds terrific. However, when Im pulling out of a parking lot, and Im barely on gas, the catback will go, "RRRKKKK".

Today, I got underneath the car to check it out, and the bolts and connections were still tight. However, I was able to put my hand underneath the connection where the GMMG was hooked up the the old system, and I was able to jerk it up and down slightly, with a corresponding banging noise where it was making contact with something.

Has anybody else had this problem? It was a GMMG system that we bolted up on par with the directions, so maybe somebody else had the same problems.

BTW, the system is badass. Well worth the money.

RevGTO

iTrader: (12)

Check for contact with the heat shield. It may need to be bent a little out of the way. As for it being badass, after I installed mine, I did a drive-by for my non-automotive-enthusiast wife, whose response was, "That is awesome!! Deep and rich!" I don't listen to music much anymore - I'd rather just hear my exhaust.

Z28Venom

iTrader: (13)

Check all of your heat shields.. and get that y to i section taken care of.

technical

The connection where the cat-back meets the y-pipe will become loose if the clamp is not "cranked" on there really tight. Fit a small piece of wood or something under the pipe and over the crossmember. Then wrench down on that clamp until your arm hurts. Or use an impact wrench like I did.

Worm

iTrader: (2)

Try tightening it with air tools if you haven't already. Or a long wrench if you don't have air tools. Things that vibrate like exhaust tend to loosen up on their own.

ls1_doc

iTrader: (6)

Sometimes on those types of crossflow mufflers the inlet pipe and the tail pipe rub on each other and bang. A simple tack together will solve it if that is it.

Wino

iTrader: (11)

Did you check to make sure it wasn't hitting the G-load brace? They do that sometimes.

DaddySS

Most common problem is where the I pipe meets the muffler section and goes over the axle. If they are not tight they'll sag and the pipe will hit the brace - reset it, tighten it again.

2002 Trans Am

Yup def check where the exhaust goes over the axle, there is a heat shield there that needs a little bit of a beating.

Went through hell with it when I installed my Corsa, but all is good now

guadofreak

iTrader: (1)

I would make sure you are not using the crappy U clamps and get some nice band clamps(bought $10 @ napa) and crank them down with an impact gun. They tend to come loose and the u clamps will bend the crap out of the pipe. Mine use to come loose till Mr. impact gun paid the clamp a visit.

WS6freak

iTrader: (3)

At the end of the car, close to the diff, check the brackets that support the exaust through the rubber pieces. They tend to snap out if the bottom bolts aren't tight. It happened to me but I just re-checked everything and there are no rattles at all.

GMMG ROCKS!!!

David 2002 WS6

iTrader: (7)

My car has the GMMG catback and it started to do this too. A slight rattle at low RPMs like when moving from a stop but other than that there is no weird noise. I jacked up the right rear wheel and saw the exhaust system was barely touching the heat shield in one spot, so I bent it away with my finger.

I also noticed that when my car is idling at a traffic light the engine seems to have vibrations as if the motor mounts are bad. I put my hand under the GMMG "I" pipe close to where it connects to the "Y" pipe and I was able to bounce it up and down a few inches. I didn't crank down on the bolts of the "U" clamps as hard as I could with my hand tools when I installed my GMMG catback because I was afraid I'd crimp the nice round piping. The next time I get under the car with it on my pair of Rhino Ramps I will try to remove any slack with the piping by loosening the "U" clamp connections, pushing the pipes together again, and tightening the "U" clamps with all my might. Stay tuned for an update...

By the way I did these things when the car had not been driven for a day. Remember the exhaust system components get wicked hot and be careful under there!!!

02_CETA_ws6

iTrader: (6)

ive got the gmmg and had to bend the shield above the rearend.

LS1vazquez

Hey people. Sorry it has taken awhile, but I want to go ahead and give you an update.

I went ahead and ran my car down to Manvel Muffler in Manvel Texas, and the guy was able to get my car up on the lift. He inspected the system, complimented me on the GMMG, then asked me what the issue was. I told him what I thought it might be, the "I" pipe, and he checked it out.

He went ahead and took out the ol' air gun and loosened the bracket. He repositioned it to cover up the little "slits" on the side of the pipe, and then he went at it. "BRRRACCCK" went the gun. Damn, I had no idea a bolt could get that damn tight. He did it again for te other connection, and then he let the car down.

What really surprised me was that when I asked him how much I owe him, he said, "Nothing man, I really didn't do anything." I was shocked. Totally unlike what you hear nowadays.

So if you guys are in the south houston area and need a good muffler shop, its worth the drive to Manvel muffler. The guy is a way straight shooter.

David 2002 WS6

iTrader: (7)

Thanks for the update!

So now the rattle and banging noise are gone, right? Did you have any engine vibration due to the exhaust system before getting the clamp at the "I" pipe tightened with the air gun, and if so is it cured now?

I think I will use my breaker bar to crank those "U" clamps tight!!!

David 2002 WS6

iTrader: (7)

Today I backed my car up onto a pair of Rhino ramps, loosened the rear clamp where the I-pipe meets the muffler section, used my jack and some jackstands to hold the pieces tight, and tightened that clamp as hard I could. Then I did the same for the clamp where the I-pipe meets the Y-pipe. A test drive later I found the vibrations are barely noticeable.

So when installing the GMMG cat-back, make sure to tighten those two clamps really, really well...!

RahuL

iTrader: (10)

It's probably an issue with the over axle pipe and the heat shield covering the gas tank. Check that one out. A lil pry bar and some elbow grease should cure this...

I've had the same issue with my GMMG!

Bearcat Steve

I had the exact same problem except I have SLP's Loud Mouth catback. I looked for the problem for a LONG time. It turned about to be a split in the ypipe where the two "sides" are joined at the sharp angle. A little bit of spot weld and everything is fine.