Odd noise diagnosis help needed

[Spittybug]

I figure that a better bunch of diagnosticians than Delorean owners doesn't exist.

Infiniti G35 sedan. ~38,000 miles. Automatic. In excellent shape.

I seem to have developed a bit of a "wub, wub, wub" kind of noise. Kind of like a hollow, echo kind of sound. Low frequency. Not all that loud, but this is such a quiet car normally that it has become noticeable.

Gets louder and more pronounced as I slow to a stop, but is unrelated to applying brakes - rolling to a stop or braking, same sound. No pedal vibration at all.
Definitely related to speed, but not engine speed - wheel speed.
Same whether I put in neutral and come to stop or keep tranny engaged.
All tires at spec air pressure. Good tread and even wear on all 4. No nails or other damage, but a least one has had punctures repaired with plugs. I think noise predated that however.
Does not sound metallic in any way. Not a grinding.
No steering wheel shimmy (balance) nor any pulling.
I've had it up on the lift and spun all the wheels by hand. No bearing noise at all. No slop, no play.
I can't say with 100% certainty, but it seems like any "bouncing" of the car (uneven road) makes it more pronounced.
I don't recall any incident or sudden start to it.
The tires are Dunlop Sport Signatures.
Road surface doesn't seem to matter.


I'm not positive, but it sounds like a driver side front noise. Next step will be to rotate front to back and see if that makes a difference. The type of noise really leads me to believe it is somehow tire related, but they all seem in great shape.

Any suggestions? Thanks.

[Dangermouse]

Have the wheels been rotated (front to rear, side to side) regularly?

If not, or even if so, look for strange wear patterns on the "blocks" of rubber (in the pattern) on the tread, or feathered edges to the pattern.

I had a similar sounding problem where every third "block" was worn differently on a car that the wheels hadn't been rotated, so the tire wear wasn't even. It would depend on the extend to wear also. I ended up replacing the tires and voila, problem solved.

[I am baby-sitting a Tahoe at the moment with oversized tires, and it has the same problem. Need to advise the owner to rotate ASAP.]

[dmc6960]

If the tire idea doesn't pan out, I'd suspect wheel bearing. Its just not bad enough yet to notice under no load. Try taking a few hard corners while coasting at a slow speed. Should help identify the side.

[DeMopar]

If the tire idea doesn't pan out, I'd suspect wheel bearing. Its just not bad enough yet to notice under no load. Try taking a few hard corners while coasting at a slow speed. Should help identify the side.

I agree. I was thinking bearing the whole time I was reading. Does seem kind of strange for the car in question, but the noise can start to happen before any play in the bearing is evident. Recently experienced this on another car of mine. If noise gets noticeably worse that's one way to tell for sure...

[Spittybug]

I too was thinking bearing, hence the spinning on the lift. I haven't noticed any left versus right differences, but will try and do so. Wouldn't that sound metallic or crunchy though? This is definitely a "wub wub" type of noise....

[Bitsyncmaster]

Look at the tire sidewalls for a deformed area. It's rare but a belt can break or move and make the tire out of round.

[DMCMW Dave]

Is that a rear drive car? If so check the driveshaft center bearing.

[Spittybug]

I've done a bunch more googling on the subject and it seems the car may be prone to feathering the tires. I ran my hand across the treads in both a clockwise and counterclockwise direction and noticed a difference in the leading and trailing edges of the "blocks" that make up the tread. I'm going to rotate and see. Not like a D with different sized tires, so I'll move fronts to back, and cross the backs and move them up front.

Yes Dave, it is RWD and one of the posts I read was indeed solved with a transmission input shaft bearing replacement. His symptoms sounded similar so it is one the list after feathered tires. Wheel bearing noises (as described by others) were more metalic, whiny and worse at speed.

With the daughter home from college and my son now having a car, I look like a used car lot. I have to juggle everything around to get the D out of the lift bay slot and get the Infiniti in there. Oh what I'd give for a 6 car garage! Next house will be 2 bedrooms, only 2,000 ish sqft, but a huge workshop and 6 bays!

[Bitsyncmaster]

Come to think of it.....My wifes Impala did the same thing a few years ago. New tires took care of it.

[Jonathan]

Just a thought here, but a few years ago at a job site, some pranksters put a couple zip ties connected together on a coworkers pickup truck. They tied it directly on the rotating shaft going to rear wheels. When you said it wasn't dependent on braking but was dependent on speed, this came to mind. There could something wedged up in there like a dead squirrel or something!!

[Spittybug]

LOL.. No dead squirrels that I can see. I did check to see if the plastic underbody cowling was perhaps flopping around and resonating though. Nope.

[Dangermouse]

May I suggest that you cross the fronts when you switch them to the back to get them turning in the opposite direction to what they are today.

Not sure if you would see an immediate improvement or whether it will take a few hundred miles.

[Spittybug]

I was wrong. The front and back are slightly different. 125/45R18 and 145/50R18. (I think I got that right from memory). In any case, that means I only did a cross, not a front to back. YES, there are still those that believe you shouldn't cross radials (not directional) but there is plenty of documentation to say that it is perfectly fine to do. The tread is still plenty good so I want to even them out and keep going. A test drive down the road and the noise was appreciably less, so I believe the mystery is solved. Hopefully a few miles on them will make the noise go away completely.

Thanks for all the help.

[Dangermouse]

I'm going to guess they are 225's and 245's and not 125/145's unless you are sourcing your tires from a Citroen 2CV

[Spittybug]

I'm going to guess they are 225's and 245's and not 125/145's unless you are sourcing your tires from a Citroen 2CV

Thin racing tires like on a 10 speed bike.

:mallet: