Help with noise diagnosis

[DSMtuned]

I posted this on CODSM and thought I would see if you guys had any ideas too.



How's everyone doing today?


I'm hoping you guys can help me brainstorm on what my drivetrain noise could be. I've had a noise that's been intensifying over the last couple months. I'll try to describe what I've gone through in narrowing down where the problem is.

Currently the sound is *similar* to the rotational noise you get in a bicycle when a wheel is out of true and the rim touches the brakes each time the wheel goes around. This can be heard during deceleration, but is most pronounced when under load, so like when I'm in a higher gear at low RPMs and giving it some gas. I can't tell if this is because the car is more quite under these circumstances so I can hear the noise, but that's what I'm assuming.

The noise was fairly quite at first. I thought maybe I should just change my tranny fluid. I did that and noticed no chunks or unusual discoloration in the old fluid. No change in the sound with the new fluid. I then started to think the sound was some exhaust leak because of the way it was louder in a higher gear when the engine was kind of lugging. Under the exhaust mani heat shield I found a turbo bolt had backed out of the manifold. I replaced the mani to turbo gasket and all four bolts. No change in the sound. I noticed that my EGT gauge probe was leaking and puffing exhaust onto the bottom of my hood. I took the probe out and replaced it with a plug. Sound continues.

The above was over the last couple months. Now the sound is much more obviously a drivetrain noise. No noise at idle, when the clutch is depressed, or when the car is coasting in neutral. The noise is present in all 5 gears and again, is most pronounced when the car is lugging under load. I went to a dry parking lot and drove around in circles in 1st, 2nd, and 3rd. Turning does not change the noise.

Any ideas? I'm stumped.

Thanks!

-Craig

[v413nc3]

It's hard to say but it could be a number of things related to your clutch or crank also. You state that with no load the noise is not there, and it also disappears when clutched in/placed in neutral so it very well could be transaxle related but I've seen some odd noises in clutches go away when clutching in/in neutral. It's worth dropping the transmission to look at your clutch/tob/flywheel just in case. Also is this a first or second generation?

[hisandherturbo]

The biggest thing that caught my attention was no noise when the clutch is depressed. If this is true at any load/speed, then it reminds me of something that happened to me. I had a 2600 and the 4 rivits (bolts) that are in the center by the springs all popped out of place, the car still drove, worked fine, lucky for me had to drop the tranny again and noticed it before something happened. Probally not the first thing I would look in due to the labor involved, but once you know all fluids are filled and good and nothing is rubbing or loose bracket under the car vibrating, that might be my next step.

[mitchel63]

I had this EXACT same problem! For 2 years....

I wasn't super worried about it because the car drove fine. Last summer I pulled the tranny thinking that this noise HAD to be the TOB. TOB seemed fine when I got in there. However, the clutch fork seemed to have excess play over the ball, so I replaced both of those along with the TOB and a new ACT street disk since I was in there. It seemed like the noise went away or was at least quieter for a couple weeks but I think that was just wishful thinking. A couple months back, the noise became horrible while driving on the interstate and after a few miles, the car would no longer stay in gear. I pulled off the road, got it towed home, and forgot about it for a few months. Last week I took my tranny down to Jack and we tore it apart. The bearing on the intermediate shaft had pretty much exploded! My thought is that the bearing was getting worse and worse for years, making more and more noise until it eventually came apart. I should be getting it back next week sometime and my car should be running the week after that. I'll definately let you know if a rebuild cured my noise. If it doesn't.....I'm going to shoot myself in the face.

My thoughts on it were that if the car was driving fine, not too much worry. No regrets on that, but when it finally went, it took a couple gears with it....food for thought.

[DSMtuned]

This is on a 1g. The new 2600 pressure plate and ACT disc have about 6k miles on them, as do the Mistu throwout, machined stock flywheel, pivot ball, and fork. The slave cylinder and clutch master cylinder are also new within the last 3k miles.

Mitchel63 described exactly what I am worried about. If I let the problem continue, then it could destroy other stuff and cost a ton of extra money.

Thanks for the input.

-Craig

[NJpearl94]

I have had similar noises ever since running the ACT 2600 combined with a welded center diff. I only hear it on a decel though. I have heard of a few other people with similar set ups having the same sounds. That being said I did have catastrophic failure to the main shaft cluster in the transmission about 10,000 miles ago and had the noise before and after. I am hoping they are not related.

[mitchel63]

My noise is gone....I have to conclude that that bearing had been on it's last lg for quite some time...

[DSMtuned]

Welp my noise was the intermediate shaft bearings in the tranny. Nice and fretted. One of the bearings came apart in Jack's hand.

The tranny is with Jack in the Springs getting a nice refresher. Umm double syncros, umm 4-spider center diff...:D


-Craig