Drivetrain noise.

[1990EclipseGSX]

I have been dealing with this problem on my 90 GSX since I bought the car in '02, and it is really starting to bug me.

The car makes a grinding noise when decelerating in gear only. The noise is not really metallic sounding. If I press the clutch in, the noise goes away. If I put the car in neutral the noise will also go away. It is not a constant noise, it kind of gets louder and quieter as I decel. The noise is especially prominent when going down a hill in gear with no throttle. However, with any kind of load on the driveline while on the throttle, the noise goes away instantly. I can feel some vibration through the pedals and seat while decelerating when the grinding is occuring.

To fix the problem I have tried:
-Checking the fluids in the rear diff, tranny, and T-case.
-Two different trannies. One from a donor car and now a rebuilt tranny from Jack.
-Three separate T-cases.
-Replacing the entire driveshaft.
-Swapping to a 4-bolt rear.
-Two flywheels. One Fidanza, and now the chromoly one that came with my PTT twin disk.
-Two clutches. An SBR 3500 and now the PTT.
-Replacing the TOB twice.
-Replacing the clutch fork and ball.
-The engine was rebuilt as a 2.3L a few years ago, and a different crank did not help either.

I am running out of ideas. Pretty much the entire driveline has been replaced, and nothing seemed to make the noise change or go away even for a short period of time.
Any ideas or suggestions are appreciated.

[yokotabrat]

Have the driveshaft carrier bearings ever been replaced? I can't think of much else.

[1990EclipseGSX]

Have the driveshaft carrier bearings ever been replaced? I can't think of much else.

They have never been replaced with new ones. I filled the ones on the old driveshaft with silicone, and that did not help. The carrier bearings on the driveshaft in the car now have not been replaced to my knowledge.

[ba109296]

It could be a number of things.
transmission
driveshaft out of balance
carrier bearings
wheel hub/bearings
u joints

You can check the u joints and carrier bearings. If you hold one side of the driveshaft and try to move the other side you should get absolutely no play in there. If you get any then you need to replace said part.

[1990EclipseGSX]

It could be a number of things.
transmission
driveshaft out of balance
carrier bearings
wheel hub/bearings
u joints


I am 99% sure it is not the tranny. This is the 3rd tranny I have had in the car now, and the noise has been there on each one. I'm pretty positive it is not a wheel bearings or hub either. I had a front wheel bearing go out once and the noise that made was always there, regardless of being in gear or on the throttle.
I replaced the front U-Joint last year when I replaced the driveshaft yoke, but I will go check any other U-joints (not positive how many there are?) and the carrier bearings.

How would one go about finding out if the driveshaft is out of balance?

[ba109296]

Usually there are shops that will do it for you. Usually the telltale sign on these is the wieghts. From the factory they all have weights on them to balance them. Just look to see if you have any on there or if they are gone. You can always put the car on jackstands and run it a little to try to find it. You might not see or hear anything though since the driveline probably needs a load on it to make the noise but its worth a shot.

[mkgearhead]

Mine does the same thing. I was thinking it might be motor mounts. Maybe on deceleration the engine is rocking just enough to put an awkward load on the front u-joint or carrier bearing. I just haven't had a chance to check mine out. Let me know if you figure it out.

[wazzelby]

I had a very similar noise on my 96 and after replacing the carrier bearings the noise was gone. I would start there.

[1990EclipseGSX]

I had a very similar noise on my 96 and after replacing the carrier bearings the noise was gone. I would start there.

Would the noise go away with the clutch in or took the car out of gear?

[Jack(IAT)]

With the modifications that I see done to the car, the noise is normal. The tranny has what is called a 'sub-gear' integrated to the 3rd gear final drive. That is there to prevent gear chatter that in most cases can be felt and heard through the driveshaft under the car under light decel. Unfortunately, when the b-shafts are removed, clutch has a stiffer hub, preloads are tighter in the trans, and the engine might have a little more harmonics, it is nearly impossible to get the noise to go away. The sub-gear gets overtaken by the added vibrations from the whole system and can no longer do its job very well. I have seen people with just the removal of the b-shafts run into this problem. My brother, before we knew what caused this, replaced his whole rear end assy, driveshaft, t-case, and trans to try to get rid of the problem. It was still there. It doesn't do any harm really. Over a long period of time you will see a little more t-case shaft spline wear and chatter wear on the hub and sliders in the trans, but that's it. The tighter you make everything from the t-case back, the quieter it will get though, so changing the driveshaft bearings, t-case coupler, tighten both the rear end and t-case, and reinstalling the balance shafts will help some. I would just learn to live with it though. That's just all part of having a car with modifications.

Jack

[1990EclipseGSX]

Thanks for the input, Jack. I guess I will replace the carrier bearings and just deal with the noise. I don't drive the car that much anyway. It's more of a fun toy than anything these days.

[Kurb_Appeal]

I have a question regarding this topic. Also an input. I built an 02 WRX with LSD that made the same noise after we installed the LSD. My 92 GSX also has LSD and it makes the same noise. In the WRX it didnt make that noise till it was installed. Ive done this before so I know I did it right. I never didnt have LSD in the GSX Does this (LSD) have anything to do with the noise.(all bearings and u-joints have been changed).