2G deceleration noise diagnosis GSX manual

[MarksGTR]

Hello!

I'm excited to share that I've finally acquired my childhood dream car, a '99 GSX, and what's even more thrilling is that it's all OEM with no modifications! However, shortly after the purchase, I noticed an unusual noise emanating from the transmission area, specifically the 5-speed manual transmission.

In my quest to resolve this issue, I took it to my trusted technician, who has extensive experience in diagnosing and troubleshooting automotive problems. We embarked on a comprehensive diagnostic journey, ruling out potential causes one by one. Here's what we've discovered so far:

1. We confirmed that it's not a transmission problem by testing it with another transmission, and the issue persisted.
2. The noise isn't originating from the carrier bearings; they've been checked and are in good condition.
3. We even disconnected the driveshaft to eliminate the rear as a potential source of the noise, and it wasn't the culprit.
4. We upgraded the clutch from a lower-quality one to an Act clutch and installed a lightweight flywheel, but unfortunately, this didn't resolve the issue either.

At this point, we're still trying to pinpoint the exact source of the noise and resolve it. If you have any insights or suggestions, please feel free to share them. Your input would be greatly appreciated.

 

[Mech Addict]

There are three u-joints and one c-v joint in the prop shaft, any of which could get grumbly when wearing out. Have you checked those?

 

[MarksGTR]

Great call @Mech Addict , but

1. We even disconnected the driveshaft to eliminate the rear as a potential source of the noise, and it wasn't the culprit.

 

[idkiliketurbos]

Any videos or description of the noise? Does this happen at any specific rpms or vehicle speed? Does it go away when moving and pushing in the clutch pedal?

 

[dwb]

Is it worse during decel in gear? Do you hear it coasting in neutral? Fluid levels all good? Sprung clutch disk or solid hub?

Curious how you tested without a drive shaft. Did you modify the center LSD to make it solid? Was the transfer case still attached?

A loose preload of the pinion bearing in the rear end could be a suspect, but not sure how that would play out without a driveshaft. For that matter, loose preload or worn bearing(s) anywhere from the trans to the rear end could be to blame.

A spare trans could have the same issue as this is an issue that plagues a lot of DSMs.

 

[chrysler kid]

What condition was the transfer case fluid in?

Are you using 75w90 gear oil in the transmission?

 

[MarksGTR]

Is it worse during decel in gear? Do you hear it coasting in neutral? Fluid levels all good? Sprung clutch disk or solid hub?

Curious how you tested without a drive shaft. Did you modify the center LSD to make it solid? Was the transfer case still attached?

A loose preload of the pinion bearing in the rear end could be a suspect, but not sure how that would play out without a driveshaft. For that matter, loose preload or worn bearing(s) anywhere from the trans to the rear end could be to blame.

A spare trans could have the same issue as this is an issue that plagues a lot of DSMs.

Great questions! correct decel in gear, very light noise (livable). do not hear it durning coasting in neutral.

In the air, nothing as be modified. Yes gear oil is new and fluid is good. Great points, I will still check.

Trans that i have was rebuilt is all oem parts as we thought it was a trans issue. It was not.

 

[donniekak]

Use a stethoscope to isolate the noise.