Good morning / Good afternoon,

I need some help on identify this issue on my S, it just happened today after a 30 mins city/highway driving with a few 6k pull and one red line.

Below are some facts.

1) the noise sounds like a rattle or vibration from clutch/transmission, I only say this because it is amplified by the shift lever and shift knob.
2) the noise sounds like some sort of rattle or vibration, get worse as you step on gas when car is moving.
3) clutch petal can feel the same rattle as shift lever.
4) the car drives normal, all gears are smooth. Idle smooth without "crazy" weird noise to my ear. Power is normal.
5) I did a datalog with flashpro, nothing seems wrong on the engine side.
6) I tested the clutch slip by step on gas on 4th gear around 2k rpm. No slip.
7) the noise seems more pronounced on gear 1-4, on 5th gear it seems much less.
8) car just hit 100k miles, its a DD not a track car. stock header, HFC, exhasut, and Spoon mounts.
9) noise is louder around 3-4k, then once past 4k it seems get masked over by engine and exhaust or simply quiet down a bit.
10) engine oil level is fine. Transmission oil is not that old, I think my last change was 2019.
11) put the car on stand this morning, there is a click noise from transmission when moving rear wheels.
12) the click noise in transmission can only be hear if the rear wheels are moved back and forth, if I roll it in one direction, it click once then disappear.
13) no matter what position the rear wheel stop at, if I move it back and forth the click will appear immediately.
14) I did not find loose heat shield.
15) Axle nuts were torqued to spec.

Below are some test I have done so far.

Car is moving + In gear + acceleration = noise
Car is moving + not in gear + step on gas = very little noise, can be felt a bit by shift knob
Car is moving + in gear + deceleration(engine brake or step on brake) = no noise
Car is moving + not in gear + deceleration(engine brake or step on brake) = no noise
Car is not moving + not in gear + step on gas(revving to 3k-4k) = no noise or vibration at shift knob
Car is not moving + clutch halfway in = no noise or vibration at shift knob
Car on stand + rev in neutral = no noise
Car on stand + rev in gear = no noise

Videos to help,
In car: From bottom: On intake: Click noise from transmission:
It is leading me to believe some sort of bearing is having issue in the transmission, on the output shaft?
I think the click noise from transmission on jack stand is not right either, but I could not identify if this is the same click when car is moving, it sounds similar but once the car is on jack stands the continuously click does not appear. And this click might be the phantom knock that is keep shown up on datalogs as well.

Thanks a lot

 

Doesn't sound like drivetrain. Maybe an exhaust leak, or broken flange or cracked heat shield is vibrating.

 

Thanks, isn't exhaust leak or broken flange can be heard even car just idling? I will recheck the heat shields, there is a chance still.

Any idea if the heat shield rattling can be felt by shift lever and clutch pedal?

 

If it's vibrating it should resonate with the exhaust which has its resonance frequency around 2800-3900rpm

 

Check for a cracked lower header mounting bracket. You will need to crack the bolt loose on the block to locate the crack, it will be impossible to determine if you don’t.

 

Thank you, will keep on mind.

 

Thank you, I will check on this.

 

Good morning / Good afternoon,

I put the car on ramp this morning and removed the slightly cracked upper shield and lower header bracket, the rattling is still there.

I also unbolted the HFC from the header side, nothing seems wrong inside.
The drive shaft seems ok, I moved it back and forth there is no noise, and I can feel there is some sort of grease still absorbing the shakes.

I have been thinking, since this rattle is linked to the RPM not speed, it has to be on the engine side. If there is a spun rod bearing, am I suppose to be able to hear it on idle? or could this be the main/linking transmission shafts or even clutch?

I bought a basic stethoscope. I listened while the car is idling, nothing knocking strongly from the engine pan(was concerned about spun bearing). My plan for the weekend is to apply a bit handbrake while car on jack and running through the RPM where the rattle happened, and see if I can trigger the noise.

What would you suggest me to check at this point?

Much appreciated.

 

I am posting two more videos here. None of these is making me feel good for the day.

Revving while car not moving, clutch out at earlier section then clutch in. There is this knocking noise but not intense as when its on the road... Driving normally for a few mins. you can hear the knock.
Sorry for the long video, there are some sections I feel could be helpful to someone with the knowledge.

Thanks alot

 

It's not engine knock, make sure the clutch fork is properly seated. Has anything been done to the clutch?