engine and drivetrain Banging noise.

[SteveK535]

OK I have a random banging going on in my drivetrain. Here is the current state of my car's drivetrain related parts. New guibo, center bearing (preloaded and BTW I scribed drive shaft and reassembled drive shaft exactly as before when the center bearing was done). Transmission just rebuilt, new transmission mounts and motor mounts. I have about 200 miles on the car since the last of the items on the list above were done. Have not noticed/felt this noise until today. Looked under neath, all front and rear driveshaft bolts are tight, guibo looks perfect, driveshaft looks to be aligned by eye, reset center bearing and drove again, still there. Its definitely in the tunnel, feel it in the seat, and can feel it when I put my hand on the rear tunnel. Does not seem to be speed related, more condition related, feel it when driving straight, but accelerating, mybe in slight bends too. Also took a slow 120 degree right turn and felt it again until the car straightened out again (this was at probably 10-15 mph). I think its drive shaft to center bearing banging, but am stumped as to why. If it was an imbalance, it would be directly related to speed. To me, its more like something is shifting around. What say yee?

[02Les]

Maybe your exhaust system moving enough to contact the floor?

[SteveK535]

I know what you mean and I do get that sometimes when I first start the car, its a similar noise...maybe. I'll have to run it with that in mind, my guess is no, but I will definitely consider that and rule it out. Thanks for the response.

[eurotrash]

I'm gonna go with exhaust as well. What system is under there?

[SteveK535]

OK this is one of those "you know you're tired when" entries. Everytime I start the car, the exhaust bangs on the tunnel. Now I post the "exhaust"ive details of the exact same noise occurring when I am driving and don't even think its exhaust related. Then you guys suggest the obvious and I say, naaa, can't be. Then I go out in the garage, start the car three times, same banging noise each time, take it for a drive and same banging noise when I accelerate on right hand bends, I start to get a bit embarrassed and run home to post my conclusions. Its the exhaust! Thanks guys!

I must say, in my defense though, that since it is winter, its not easy to get a lot of consistent and long drives in to hear what's going on and diagnose things. Since I have done quite a bit over the winter and replaced a lot of drive line parts, the number of variables I was considering got a bit large. I had to tweek the exhaust several times to make it clear when I reinstalled it. Its a BOSAL (sounds nice and throaty, but tasteful) and is definitely oversized from the original, I forget what size the pipes are, but it is a bit temperamental to get in just right without hitting. Anyhooo...

[c.d.iesel]

loose stuff in the trunk ?

loose trash under the back seat ?

[SteveK535]

No junk in the trunk, or trash under my ash!

[jgerock]

Double check the exhaust pipe section that goes over the rear crossmember. Getting that section tilted to the correct angle while tightening the (3) resonator-to-downpipe bolts is pretty difficult when you are installing it yourself.

If that section is banging on the crossmember, it may also be rubbing the left inner CV joint.

[SteveK535]

Thanks Jim, will do!