Vibrating Noise, Rumors or Truths?

[b-morr]

1990 Eagle Talon

I'm almost done completely rebuilding my 1g. I bought it and on the drive home, about 3 hours, it broke down. But on my way home any time I took my foot off the gas pedal with the car still in gear and the car moving, it would make a vibrating noise like metal to metal contact. Same would happen if I engine braked. After research and talking to others I came up with some possible problems. Now I'm tight on money and need the car running in a weeks time.

This is what I came up with.

1. Driveshaft needs rebuilt

I don't have the money to do it right now, and don't want to spend the money if I'm not sure its going to fix it at this time.

2. Bad rear differential.

I had a lot of people telling me this was the problem. Eh, is what I think of that, I drained the fluid out of it, and the fluid looked brand new despite not being replaced since two owners ago. There was some extremely small pieces of what I guess was metal on the magnet that's on the drain plug. So small it felt more like fuzz than metal. I would think that the diff would be good then? I could be wrong.

3. Tranny and Rear Differential don't match up.

This I know nothing about, except what I rear in one topic on this site. The tranny is a C51PH, which I believe is a JDM one. Now what I read was that the C51PH tranny and the 3bolt rear don't work together. But a 4bolt rear does. I have no idea about this, and only could find it in one place, which is why I want to verify. Again money is a issue along with this car needs to get done.

4. Its just going to happen..

I read in a few threads that when you remove the balance shafts and have a lightened flywheel that you will get these vibrations when engine braking and its just going to happen no matter what (I installed prothane motor mounts, so I figure it will happen even more now). Both of which were done to the previous engine that was in the car, and with the new engine also.

So...

It would cost me about the same to rebuild the driveshaft as it would be to get a 4bolt rear, I do not want to do them both. So I'm at a loss, which one would you think the problem would be?


EDIT*
I just saw a post (http://www.dsmtuners.com/forums/dri...e-during-decelartion-coasting-while-gear.html), in which he is pretty much having the same problem. I found another thing, that with aftermarket flywheels and clutches they can be unbalanced. The car had some no name PP and 3 puck disk. The PP felt like a ACT 2600-2900, and the flywheel I believe is a Fidanza, its about 8lbs. I put in a new ACT 2900 PP and street disk, along with the old 8lbs flywheel. If I cant decided on what to tackle, I may just drive it and see if the noise has changed at all from the new PP being put in. I would guess then that the flywheel and PP not being balanced together have some play in the vibration.

 

[BrokenTsi]

I dont think its the clutch at all. I think its a problem with the driveshaft and/or a component of the driveshaft.

Its definitely not the balance shafts.

 

[tenn-gsx]

Gheck the rubber on your driveshaft hangar bearings. If they move too much in the housing it can cause a horrible growling when unloaded. If there is alot of play it will cost you less than $20 to fix it as long as its the rubber part and not the actual bearing.

 

[red1993gsallmt]

i have the same thhing. i rebuilt the driveshaft, balenced it but know luck. i think it has to do with the prothane mounts and no balance shafts because its only between certain rpms, and goes away when the clutch is pushed in and the rpms drop. i just leaned to live with it

 

[viprez586]

It's likely due to the stiffened springs on the clutch disc. The manufacturer took this into consideration when designing the vehicle - which is why you never heard it before. On decel in gear: the hub springs on the clutch disc are getting "shocked" or "pulsed" from the crankshaft vibration of decel(or rotation) resulting in drivetrain "Whomp"/"Whap"/"Growling".

Balance shafts are designed to balance out harmonic noises and vibration from the rotating assembly. Eliminate them and your result is noise and vibration. Both which are associated with each other.

Mine has it, EVOs have it, tons of people have it. Just turn up the music.

 

[b-morr]

It's likely due to the stiffened springs on the clutch disc. The manufacturer took this into consideration when designing the vehicle - which is why you never heard it before. On decel in gear: the hub springs on the clutch disc are getting "shocked" or "pulsed" from the crankshaft vibration of decel(or rotation) resulting in drivetrain "Whomp"/"Whap"/"Growling".

Balance shafts are designed to balance out harmonic noises and vibration from the rotating assembly. Eliminate them and your result is noise and vibration. Both which are associated with each other.

Mine has it, EVOs have it, tons of people have it. Just turn up the music.

Thanks for the info, I'd be happy to just live with it if I knew that was the problem. I guess I wouldn't really know unless I fixed everything else.

I would really like to get some input on the tranny working or not working with the 3bolt rear

 

[BrokenTsi]

If the ratios were off for the transmission and the rear end, one of the two would have gone up in smoke real quick. When I bought my first DSM, it had an auto rear end in it. It made the 4 hour drive, but soon after that, the rear end locked up and the viscous coupler in the trans burnt out.

 

[b-morr]

Yeah, he said he drove the car on it's setup for about 10k miles so I'm sure they are fine. But he lie about a lot of stuff so who knows. It felt fine besides the vibration when any amount of engine braking was done.

When I bought the car the guy said it was because th exhaust was rattling, but I don't see where it would be. It is missing 1 rubber mount, but when I move the exhaust it doesn't make any noises.

 

[BrokenTsi]

You'll be surprised how much an exhaust can move. The cat-back is pretty close to the rear diff, especially if its bigger than stock.

 

[b-morr]

You'll be surprised how much an exhaust can move. The cat-back is pretty close to the rear diff, especially if its bigger than stock.

That could be a possibility, wish I could see down there while driving. The missing mount for the exhaust shouldn't be causing that though I wouldn't think, it's just one and there's one righ on the other side obit connected.

 

[Lofty]

I would REALLY check the tranny and the rear end matches up. This is what it was like on my car. I mean YEAH THE EVO 1st gear was EPIC! But then it blew out my viscous coupler, my center diff and almost everything else. D:

That or the clutch disc just likes to chatter. However, i remember specifically the noise my car made with the mismatched trans. Sort of a quiet ish whirring sound. A little high pitched but just basically sounded like a jet in the distance.

Carrier bearings are more of a vibration thing than a noise thing. But that + a springless clutch disc with an ACT2100 is quite the decel feeling.

 

[92AWDTalonTSI]

My Miata did the same thing. Turned out to be a Universal Joint. It would also make the sound when at high speeds on the highway. Like 75-80. I would not recommend testing if yours does it too. Try moving the drive shaft to check for play. It has 3 U-Joints IIRC.

http://www.dsmtuners.com/forums/drivetrain-tech/314363-resolved-drive-shaft-u-joint.html

 

[Ceddy]

The car had some no name PP and 3 puck disk.

Pucked disks chatter on decel and engine braking.
The lower amount of pucks the more they chatter.
A 3 puck is as chattery as they get.

 

[94awdcoupe]

This issue is from removing the spring center disc. Very common problem with twin plate clutches. Whats happening is the engine harmonics are transferring through trans and into the drivshaft where the vibration is heard. light weight flywheels also pronounce the issue and may even cause some noise with spring center clutches. . heavier flywheels absorb some of the energy. Its not a clutch or flywheel imbalance issue.

 

[b-morr]

Pucked disks chatter on decel and engine braking.
The lower amount of pucks the more they chatter.
A 3 puck is as chattery as they get.

Must have been it, only thing I changed in the drivetrain was put a street disk in with a 2900PP, and it no longer makes the sound.