Rattling sound from drivetrain

Ok so I am 800 miles into the breakin on my transmission and just got back from my 3rd trip to the desert. I just noticed the other day when I am doing about 25-30mph in 5th gear I will get a rattling from under the car. I haven't really checked anything out yet. But I was wondering if somebody might have some ideas about what it could be.

I plan on jacking the car up and seeing if there is anything rubbing or hitting, like the exhaust and drive shaft. I don't see it as being the clutch or the transmission, not so sure about the transfer case though. I guess all I can do is drain the fluids and see if I have any metal chunks. I usually drive the car pretty hard, so I never hear this sound, because I am shifting into 5th gear around 45-50. Since I am breaking it in though I have been driving it easy.

Anyway I don't really care if its just an annoyance thing, because I can deal with the sound. I just hate to think of it as something slowly getting destroyed. Does anybody have any ideas? What are the symptoms of a bad transfer case? I also read of one other person having this problem, I guess he had the problem ever since the car was brand new, took it to the dealer a number of times and they never could fix it.

If it's under the car it could just be a grounding strap for the O2 sensor rattling against the exhaust... Or possibly a broken hanger rattling off the exhaust too... At least its a place to start lookin.

If it were something like that, then it would be ok. Is there any kind of noise like that which would be caused by the transfer case or driveline? I was trying to hold off on changing all of the fluids until the breakin was finished. But now that this has showed up I think I am just going to do it all tomorrow for some peace of mind. If there was any kind of problem, I would think looking at the oil would be the most obvious sign. Of course I hope that it is like you said just the exhaust hitting on something with the vibration of 5th gear and 30 mph. Of course I am a worrier anyway so the worst case scenario is always the problem in my mind.

5th gear and 30mph, I'm gonna guess just something non-important rattling... If it was something critical in the drivetrain then I would assume it to be heard at the same RPMs in every gear. Know what I mean?

Well it makes the sound at lower rpm's in 4th gear too, but not as bad. When I get it to rattle pretty good and i bring the car to a stop I can hear it just a little bit. It doesn't look like there is anything loose. When I push in on the clutch the sound goes away. The transmission is new, so is the clutch and throw out bearing. I still haven't changed the oil to see what it looks like. Any ideas?

If you push on the clutch and the sound goes away then it could be the throw out bearing... Is there a little bit of grease on it where it touches the pressure plate? If not, this will cause a rattling sound. (Found this out the hard way on mine)

If you push on the clutch and the sound goes away then it could be the throw out bearing... Is there a little bit of grease on it where it touches the pressure plate? If not, this will cause a rattling sound. (Found this out the hard way on mine)

Agreed. However, that sound would be a little more consistant across the board, not just very low in a gear. Mine used to be the same way (only when cold though). Would rattle and make noise, but when I pushed the clutch in it would go away. But that sound would basically always be there in any rpm range until it warmed up.

I would say pick it up, shake everything around and see if it rattles or anything when you do that just to elimate hangers or heat shields. Then go from there.

What clutch are you running? Most aftermarket clutch disc do not have the anti rattle springs like a stock disc does. These springs are what absorb your gear rattle from the tranny. So if your running an aftermarket disc this could be your problem. When the car is idleing the tranny is spinning and you can hear the gear rattle, when you push the clutch in the tranny stop spinning so the rattle goes away. My car has done this every since we took the stock clutch out. At idle its noticable but I have never heard it goin down the road. If it drives fine I wouldn't worry about it to much. Your tranny should have a warrenty on it since its new so worse happens and it does tear up it should get fixed free right.

Well its an ACT 2100, it came with a new Throw Out Bearing. I put a good bit of grease on when I installed it. I am confused about the throw out bearing and input shaft bearing. From what I have been reading up on, if the TOB is bad it will make noise when you push in on the clutch. The input shaft bearing will make noise until you step on the clutch and it goes away. Im still not 100% on this because everything I read up on will say one or the other. If it is the TOB though? What are the consequences of just leaving it and letting it make the noise.

That noise is terrible when it shakes like that, but like I said if I drive the car normally you don't even hear it. All of the gears shift fine, aside from the noise there is nothing out of the ordinary. I emailed TRE transmissions and asked him about it, hopefully I will hear back from him soon. There is a 1 year warranty on parts installed by him. So the input shaft bearing I guess would fall on him. TOB would be up to me.

It makes sense that the input bearing would stop making noise when the clutch is pushed bc the disc stops spinning and so does the tranny. Does the noise sound bad or is it just a knock?

http://www.youtube.com/watch?v=b_Vc7IXfdSg

Does it sound like that

That is almost exactly the sound it makes except alot quieter at idle, and a lot louder in the lower rpms at higher gear. I talked to John at TRE. He said the input shaft bearing is hardly ever the case and on a transmission that sees alot of abuse could show signs of wear at around 50-60k miles. Basically he told me to change the oil and see what comes out. If there is excessive oil shavings or silver paste then something is wrong with the transmission. But if its just the normal metal shavings then the transmission is fine.

So what do you think about that clutch chatter video? TOB maybe? Or is it just something with the clutch. Basically I am asking is it ok to leave it like this or is it something that I should look into? Like I said the TOB is brand new, I greased it up good and it's installed right.

That video is just clutch chatter, nothing wrong with his car.

Well if that's all it is then I guess Im in good shape. Maybe i will send that video to John at TRE so he knows what the hell I am talking about. Its hard to diagnose a noise by describing it. I just wonder why my buddys doesnt do it with an ACT 2600 and the same TRE stage 2 tranny. I guess everybodys car is different. So that clutch chatter is nothing to worry about then right? Im still changing the oil tomorrow just to set my mind at ease.

If it is clutch chatter then yes it fine. Still a good idea to check the oil like you said just to confirm that nothing is wrong with it internally.