rythmic noise/grind from the back end
 

I hear and feel a mild "chuffing" noise and slight grind that changes with speed of the car.

I have ruled out brakes, since it occurs with or without the brakes on.

I hear it on smooth pavement, otherwise there is too much road and car noise to hear it well. I have not been able to duplicate it with a mechanic in the car.

I have ruled out transmission, since it occurs when the car in neutral and/or the clutch disengaged.

It might be tires, but the low-speed noise and sense of grinding kind of argues against that.

Could it be differential, LSD, bearings???

Believe that some owners have had noise from the Limited Slip Diff. and did a fluid change, after that, not sure. I'd try a fluid change first and see if it helps any.

This car does not have an LSD.

Are you on stock suspension? Is it the driveshaft carrier bearing? When I first lowered it the toe was out enough to make some road noise on my way to get an alignment.

Exsqueeze me, wot?!?!?


[ame="http://www.youtube.com/watch?v=u0EOrzn7-Qc&sns=sms"]2013 Scion FR-S | Torsen® Limited Slip Differential Explained - YouTube[/ame]

Attachment 95191

Uh.......yeah it does..............

[ame="http://en.wikipedia.org/wiki/Torsen"]Torsen - Wikipedia, the free encyclopedia[/ame]

From my experience rebuilding my own diff, I'll try to chip in to the best I can. As far as I could tell on my diff, the diff gearing itself really only made noise under load (so accelerating or engine braking). So I doubt it's the ring/pinion gears. If it was the actual diff, I would think the noise would be more prominent around corners, is this the case? If it were a bearing, it would be more of a whirring noise, is that what you mean by "chuffing"?

If you are up for trying things, I'd replace the diff fluid and see if it changes the noise at all. Inspect the plug as well for shavings. A decent amount of shavings/sludge on the plug is fairly normal if you haven't changed the fluid yet.

Is it more prominent from any particular side? This may indicate axle or wheel bearing issue on that side.

Any mods to the car? Any adjustments to the clutch?

I have a strange tin can like rattling noise also. It has progressively got louder and is borderline annoying now. The noise started when I changed my tires. Someone else on this forum heard rattling from their aluminum valve stem being loose that sets in the wheel. Ill go to the tire shop and have them check it out.

Nope. No lsd. Torsen.

Torsen (full name Torsen traction) is a type of limited-slip differential used in automobiles.
[ame="https://www.youtube.com/watch?v=u0EOrzn7-Qc#t=48"]2013 Scion FR-S | Torsen® Limited Slip Differential Explained - YouTube[/ame]

Right. I forgot nobody can be wrong on the internet without being correctly in the most childish way possible. Big red print. Gold star bucko.

To the OP: do you have any sort of suspension mods? The way you describe it, it almost sounds like you're grounding out the car.

On a different note, when the noise occurs, does the car react in any way (slowing down, etc) or does the noise cause the car to vibrate?

He had already been corrected once - I thought a little visual aid might help. It has worked for me and it appears to have worked here. Perhaps I should have just used BOLD - Big Red is kinda like passing double-dog-dare and going right for the triple dog dare - so I acknowledge a slight breach in etiquette but you can't deny the effectiveness.

The car is stock the sound is like a rapid chuff chuff chuff sound at 20mph same on straights as on curves

Check your tire tread and see if anything is stuck to the tread, or if the tread is worn down too much. Check that nothing is rubbing on the wheels such as a body panel or piece of road debris. Make sure you have all of the plastic rivets that hold the liners in place. I've had the plastic under panels make a scraping/chuffing noise at speed once some wind can get behind it and make it flop around while missing some of the plastic rivets.