sound when slowing down

[L8apex32]

My car has a sound, like a soft squeal or whine - a slight grinding/wear sound - when decelerating. I notice it occasionally when slowing down below 15 mph.

I've tried to eliminate the brakes from the source. Whether on or off the brakes, it makes the sound. The brakes make a harder krsssssh sound as I have racey pads. Sometimes, the brakes squeal, which is totally different than this sound. I can cause the brakes to make sound by applying them and can get it to go away by releasing them. It seems not to be the brakes.

I suspect either a rear wheel bearing or a CV joint. The manual says to check for looseness in the axle, which I didn't detect by manipulating it. Maybe I didn't check it correctly.

The manual says the wheel bearing can be measured for run out. I don't have a guage (I'll borrow or buy one) but with the rear wheels in the air, and car in gear, the wheels spin evenly so that I can't see any wobble. During these tests, the sound was not detectable. I also gave both rear wheels the standard top and bottom wiggle to see if there is any play and there isn't any.

I also coasted down the hill to my house with the engine off a couple of times. I couldn't cause much of a sound in a few tries like this so it isn't an "always does it" thing. But, I think on the road, its a "mostly does it". Maybe it does it more after being warmed up?

I can hear it over the idling engine on the road at slow speeds, but not at high speeds. As the car slows, the sound slows with it, ultimately stopping when the car is at rest.

Any advice as to how and diagnose this better? If we eliminate brakes as the source, what is the most likely?

Thanks for helping get my car ready for the '08 track season.

 

[NSXT]

Mine was making a noise similar to this, it was the mid-shaft bearing. It kinda sounded like a wheel bearing, but at a higher tone and not as grindy, if that makes any sense.

I first thought it was dragging brake pads or wheel bearings, but the noise was coming from under the car, not from a corner. It was loudest when warm, coasting about 40mph and driving next to a wall so you hear the echo.

Had to put the car up on jackstands, start it, put it in 1st and crawled underneath to listen to all the spinning stuff to determine the mid-shaft bearing was noisy. Stop engine, remove the little heat shield over the right inner CV, grab the CV housing and shake it around. Mine had tons of radial play.

 

[otoro]

Check your tires.

 

[L8apex32]

I borrowed a dial indicator accurate to .001 in. It shows the rear wheels well within spec, both radially and axially.

I also crawled under and re-tried checking the CVs and the inner half-shaft joints for looseness. Both CVs feel pretty tight and have just the smallest amount of rotational slop - almost none.

Radially, they are even tighter. I can't move the shafts at all up and down, relative to the joints. The shafts slide in and out a little, but I think a little in/out motion is expected.

Tonight I'll fire it up, in gear, on stands, and crawl under. Maybe I'll be able to hear something as it spins in gear.

I think it does it more when warm than cold. So, I'll probably also try a short drive to warm it up and to make sure I can hear it, then try it again on jack stands.

After that, I'll be out of ideas.

 

[L8apex32]

The sound was getting a little worse - and I was a little more sure it was the bearing. So, I took it out last night and - it is clearly the left rear wheel bearing. I can feel the play in my hands.

So, that begs the questions of why I can't see this with a dial indicator and why I couldn't feel this by wiggling on the wheel?

I have found the bearing part number. Its NTN HUB098-13. Unfortunately, according to NTN, this is a proprietary bearing and they don't sell them individually.

On the better news side, they say that some of these bearings are more than $100 and some bearings cost near $1000. One person from NTN suggested that $250 or so for a bearing of this type pressed into an aluminum NSX specific hub isn't necessarily a bad deal. But, she couldn't look up the exact bearing specs so its hard to say.

I just received a call from Acura and they say that my hub was spinning inside the race and has been scored. Maybe that makes sense as to why this was difficult to diagnose?

This news just added $181 to my total (which is now near $500). Perhaps there is a way on the next gen NSX for having the ability to replace a wheel bearing and not having it cost $380 in parts.

 

[NSXFRIEND]

I just received a call from Acura and they say that my hub was spinning inside the race and has been scored. Maybe that makes sense as to why this was difficult to diagnose?

This news just added $181 to my total (which is now near $500). Perhaps there is a way on the next gen NSX for having the ability to replace a wheel bearing and not having it cost $380 in parts.

That is reasonable to me, a BMW wheel bearing replacement on an E46 can be upwards of $700-800 depending on dealer, they say it requires a special tool

 

[docjohn]

there are a lot of posts about wheel bearings I just decided to use this one.I must thank Larry B for showing me how little play is needed in the 3-9 oclock wheel shimmy test.I have been slowly over time getting more road noise/hum from the rear of my car.My tech just told me that both bearings are toast and so bad that the whole hub assembly needs to be replaced,,,,so make sure you check your wheels for play-only need a mm or less of motion.If Larry had not shown me I would have never known how subtle it is.

 

[RON98]

That is reasonable to me, a BMW wheel bearing replacement on an E46 can be upwards of $700-800 depending on dealer, they say it requires a special tool

bmw prices.

if the hub is pressed on then yes you'll need a special tool, ie: large slide hammer or hydrolic press.