Noise from front of manual transmission.

[helpme]

Irregular whirring noise from clutch area. Louder when its cold (in the morning) most noticeable at idling. Clutch seems to work OK but pedal appears to be at the the top. NOT slipping. Loose Y pipe maybe? Has 285K on it. Clutch replaced 10 years ago. Thanks.

 

[RonD]

Does the noise change when clutch pedal is up or down?

 

[helpme]

No. I read somewhere it might be a flywheel problem.

 

[helpme]

Checked the Y-pipe. Its OK. Could it be the fingers of the pressure plate riding around on the clutch slave making that noise? Thanks.

 

[RonD]

Yes, failing throwout bearing or pilot bearing but these will have a noise change depending on clutch pedal up or down

 

[helpme]

Its a low rumbling noise. I think its pressure plate or flywheel. But it doesn't change with pedal position.

 

[corerftech]

Bearings can make a low grumbling noise like you describe. All bearings (roller/ball) in any service position. TO and pilot are in the vicinity.

Wheel bearings especially are a good example of that grumbling.
Just as an example.

 

[RonD]

More likely to be internal transmission issue if noise doesn't change with clutch pedal position

Do you still hear the noise when coasting in Neutral with clutch pedal down all the way?
And does the noise change if still coasting and you put it in say 3rd gear, clutch pedal down?

And does the noise change while coasting in gear with clutch pedal down all the way, and you REV the engine?

Flywheel and pressure plate can only spin at engine RPMs
Transmission can only spin at rear wheel speed(in gear)

If noise only follows rear wheel speed then its a transmission issue
If it only follows engine RPMs then flywheel/pressure plate

 

[4x4junkie]

My '94 has made a noise similar to what has been described here ("irregular", "rumbling", "most noticeable at idle", etc.) and audible outside up to about 10 feet away. A friend called it "gear rollover noise" and could be resonating through the exhaust heat shields or frame or ?.
Checking the trans fluid, I found it to be bright pink, so I just kept an eye (ear) on it after I first noticed it. It never did get worse over 90K miles all the way up to when I put the truck in storage a couple years ago. I've noticed the same noise on other M5ODs, though none as loud as my '94. The noise however does go away when the clutch pedal is down (clutch released), so that part isn't quite fitting here (I can't think of any noise that would be internal to the transmission that isn't changed by pedal-up vs. pedal-down unless the clutch disc is dragging slightly, in which case it would still be affected by putting it in gear).

Regardless, thing to check is the fluid condition... It can potentially tell you a lot about the condition of the transmission. It should be anywhere from a bright pink color to a deep red or purple with maybe a slight brownish tint. If it's black, it probably hasn't been changed in forever. If it grayish or metallic-looking, the transmission likely will need some attention (rebuild or replacement).

 

[helpme]

Thanks. Seems to change a little bit with engine rpm (clutch dis-engaged). Transmission fluid was changed about 3 years ago. Checked it and it was full (purplish color) recently.
Hope its not my input bearing to the transmission.

 

[RonD]

Input shaft bearing is not a common failing, but a known failing, on any manual transmission because of "how it works"

The main thing is that the Crank shaft and input shaft, at the transmission end, are PERFECTLY ALIGNED
This is done by bell housing being perfectly machined to center the input shaft bearing
And alignment dowels on bell housing and block are not worn down, the bolts just hold the bell housing and block together, not precise enough for true alignment, that's the point of the alignment pins or dowels

Then there's the Pilot bearing that holds the end of the input shaft in prefect alignment so the shaft spins true

Lots of "prefect stuff" to go wrong, lol

If there is a slight misalignment then you get a vibration at the input shaft bearing end, crank/flywheel has too much mass(weight) to vibrate because of misalignment, so transmission end gets the brunt of vibrations
Its not a vibration you would feel, just there for the bearing to deal with
After several transmission/engine separations over the years older vehicles can have misalignment
Or a failed Pilot Bearing that's not changed right away, or noticed

So input shaft bearing can fail over time

 

[alwaysFlOoReD]

I remember reading about some a4ld trans that were machined wrong and would have problems with the pump, and maybe bearing? It's been a long time since I read that and dont remember exactly where it was posted. I don't think it was TRS.

 

[RonD]

+1 ^^^

Yes, there were issues with A4LD bell housings, causing misalignment, but it would cause front seal to fail and ATF would start coming out pretty fast, which would hasten a repair long before bearing damaged

Similar to Rear Main seal failing on engine side, you would fix it, hopefully before bearing damage, lol.