Hi! My 2007 Civic Ex (automatic) has been making a noise for probably close to a year now. Whatever is wrong isn't making my car drive badly/slower or even loudly, but something is wrong. At first I thought it was the transmission. See, when I'm at highway speeds and drift, especially when my car begins to downshift, it makes this jumping noise like it's shifting in between gears. Sometimes when I start it, it makes a light grumbling/vibrating noise for like 3 seconds and stops. A friend suggested that it could just be that the exhaust pipe might be slightly disconnected from the catalytic converter, or somewhere up there, but no one has looked at it. I've completely disconnected that before on a different car, and that was way louder than what I'm dealing with now, so I know it's not hanging down. Does this sound like it could be the problem, rather than it being the drivetrain/transmission? And about how much would that cost to fix?

Ps. I don't know squat about cars

 

lift the car up on a good set of jack stands and have someone start the car up. then the other person can listen for the noise to at least try and pin point a location for futher diagnosis. I'M SURE YOU KNOW BUT BE VERY CAREFUL ESPECIALLY SINCE YOU WILL BE STARTING THE CAR UP. SAFETY FIRST. TAKE OFF THE FRONT WHEELS OR JACK IT FROM THE FRONT SO THE CAR WILL NOT MOVE UNDER ITS OWN POWER.

 

Very difficult to diagnose the problem you have, you didn't indicate what type of noise "grumbling/vibrating noise", is it exhaust noise or transmission clunking noise?

 

It sounds like the noise is coming from the upper middle area of the car, like right under where my gear shifter thing is. (about a 1/3 of the way from the front of the car). That's why I was thinking it's where the cat attaches to the exhaust pipe. To me, when I'm driving it sounds like it's almost picking up air...the car makes up and down noises (think vrrrmVRRRRMMMvrrm)

 

sounds like you're either missing bolts/nuts somewhere, or have a blown gasket. If you can get under the car with it started, someone else can put an oven mit over the tailpipe and if there's a leak or blown exhaust gasket you'll see it coming out.

or by the way you described the noise at highway speeds, it could be the transmission mount(s)...? idk though

 

I would also check the heatshields on the cat those are known to rust off the stock cats if there is high salt use on the roads and coastal areas as well