Whine/Rumbling noise coming from the rear axle

[CB72]

I'm heading to the NSX track meeting in Spa-Francorchamps and I noticed a whine coming from the rear of the car:frown:
The whine is linked to the speed of the car and doesn't change when disengaging the gears.
When you get to a stop the whine changes in a kind of a grumbling noise?
I have the 5 speed gearbow with the OS Giken LSD that I installed a couple of years ago.
I lifted the rear of the car to allow the wheels to be turned by hand and I didn't notice anything abnormal?
The freeplay is the same as when I mounted the gearbox as far as I remember and it's identical right an left.
There is no oil leak and the CV joint boots are intact.
The wheel bearings seem OK as well with no play whatsoever.
Could the noise come from the brake pads?
I changed these recently to Performance Friction PFC 01 if I remember correctly.
I'm quite concerned about tracking the car on one of the fastest tracks in Europe and any help would be appreciated

 

[CB72]

I went to wash the car today and I realized that I forgotten to mention that I'm running Toyo R 888s...
While driving I tried to go from no load on the transmission to eitheir very slight load by accelerating or decelerating.
The noise doesn't change at all and that's what made me think about the tires!
This is compounded by the fact that I'm running with maximum toe-in at the rear and it's currently very warm over here.
Let's hope that's the real reason for the whining noise!

 

[nsxnut]

I don't think it is the tires. I take it you have the same tires front and rear. You said the wine is in the back of the car.
If it was the tires than you would hear it in the front as well.

This sounds mechanical.

Later,
Don

 

[Coz]

Sounds like one of the main bearings on the Impute or Counter shaft in the gearbox could be on it's way out.
Has happened to me and made the sounds you are describing.

>>The whine is linked to the speed of the car and doesn't change when disengaging the gears.
When you get to a stop the whine changes in a kind of a grumbling noise?

 

[CB72]

Yes, as I get to a stop the whine changes to a grumbling noise...
If it's one of the gearbox bearings could it end in a catastrophic failure or will it degrade gradually?
Coz, did you have your bearings changed immediately or did you keep on driving for some time?
I will be doing approximately another 1000 km on the highways and maybe 120 km of track time.

 

[Coz]

Thats what it sounds like to me. Mine was doing and making the same exact noises.
Mine turned out to be the impute main shaft bearing. It's the big one that holds the impute shaft in place.
There's also another big one that holds the counter shaft in place as well.

What's happening is the bearing is not running round anymore, which is the whine you hear at a higher speed when force pushes the bearing to the outer race.
Then as you slow down and stop the bearings start grinding itself against themselves which is the grumbling you hear at idle.

If the bearing totally collapses. it's going to cause whatever shaft its on to start to wobble. (If it's not wobbling already) Once this happens, the impute and counter shaft will separate and will tear your gearbox to pieces inside since all gears on the impute and counter shaft will pull away from each other, chew themselves up and spread gear and bearing fragments all thought your gearbox including your diff. You could also crack your case and or tear up the snap rings grove which also destroys your upper case even if you don't crack the case in the process.

I'm not saying this is your problem, but from the sounds of it and not actually hearing it, that would be my first thoughts.
Since you have checked pretty much everything else that's moving parts in the rear drive train, I don't see what else it could be.
You have checked the brake pads, rotors, rear wheel bearings thoroughly, correct ?

I doubt this would be the problem, but you might want to pull your speed sensors in both rear hubs just to make sure nothing is trapped in one of them. (Easy to do and check)

When we broke mine a part, that's what we found. I was lucky I stopped on a track day when I heard it and towed the car home without doing any further damage.
The bearing pieces still manged to tear up 2 gears, 2 sycro rings and some other minor bearings as well.

- - - Updated - - -

If you have a NSX manual...Look at Page 13-23 and 13-29 and you'll see the bearings I'm talking about and why they are so important and the damage they can do if one of them fail.

 

[1K2GO]

CV joint going?

 

[Coz]

Not turning when sitting at idle.
Unless I am misunderstanding what he's saying.
If the noise goes away at a complete stop, then it could very well be an axle bearing.

>>Yes, as I get to a stop the whine changes to a grumbling noise...

 

[1K2GO]

Not turning when sitting at idle.
Unless I am misunderstanding what he's saying.
If the noise goes away at a complete stop, then it could very well be an axle bearing.

>>Yes, as I get to a stop the whine changes to a grumbling noise...

Yes, I saw that, but I interpreted it to mean 'while he's coming to a stop' as opposed to 'at a complete stop'. Lost in translation?

Perhaps this is just wishful thinking that its not his trans, but I've had cv's go and they make a howling sound that changes pitch with changing speeds.

Regardless, what I would give to run my car at Spa!

 

[Coz]

It's a great thought and could very well be the problem.
Most anything other than the gearbox would be a good thing.
We'll have to wait for clarification.

Yes, I saw that, but I interpreted it to mean 'while he's coming to a stop' as opposed to 'at a complete stop'. Lost in translation?
Perhaps this is just wishful thinking that its not his trans, but I've had cv's go and they make a howling sound that changes pitch with changing speeds.
Regardless, what I would give to run my car at Spa!

 

[CB72]

Coz and 1H2GO, many thanks for your help on this issue!
It's been years that I haven't run at Spa and the disapointment is enormous as you can imagine.
As a clarification, the whine turns into a grumble when my speed approches zero.
When the car reaches a complete halt there is no more noise even in neutral with a released clutch?
I had suspected the CV joints but as I said the wheels turn freely without any noise when rotated by hand.
I wonder to what extent the root cause of the problem does not come from the OS Giken diff when you hear and feel how abruptly the wheels lock and unlock?
Luckily(?) when I bought my OS Giken LSD, I mounted it ( myself) in a spare gearbox.
My current plan is to take the car to the Honda dealership for inspection and eventually get the OEM gearbox reinstalled.
Too bad for Spa but I can maybe save the Le Mans outing beginning of August?
Thanks again.
John

 

[Coz]

My thoughts.

Coz and 1H2GO, many thanks for your help on this issue!


>>It's been years that I haven't run at Spa and the disapointment is enormous as you can imagine.
Yea, I know the feeling...I run 20 to 24 days a year on track for points and standings, any missed date is a drag.
Get used to disappointment, that's why it's called racing


>>As a clarification, the whine turns into a grumble when my speed approches zero.
OK... not at a complete stop

>>When the car reaches a complete halt there is no more noise even in neutral with a released clutch?
Thats a good sign, that means your bearing very well could be OK.

>>I had suspected the CV joints but as I said the wheels turn freely without any noise when rotated by hand.
Yes, because they are not under any pressure yet. When is the last time they were serviced ?
Pull them off and rebuild them since they will be out anyway when you change out the gearbox. I posted a thread some time ago about it, it's easy.
You can PM me and I will send you pictures and a run down on how to do it correctly with boot vents.
You may not have to pull the gearbox at all actually....

>>I wonder to what extent the root cause of the problem does not come from the OS Giken diff when you hear and feel how abruptly the wheels lock and unlock?
Depends on how tight the plates were set. Who did the install ?
How old is this Giken ?

>>Luckily(?) when I bought my OS Giken LSD, I mounted it ( myself) in a spare gearbox.
OH, well then, how many plates and how did you measure the lock up, release and backlash ?

>>My current plan is to take the car to the Honda dealership for inspection and eventually get the OEM gearbox reinstalled.
First I would take a part the axles before pulling the gearbox to see if there's anything obvious. Then.. if you don't find anything there including your intermediate shaft ..Yup, that's exactly what I would do and then open up the box and see whats going on.
It may not be as bad as you think. You may have the Giken misaligned.

>>Too bad for Spa but I can maybe save the Le Mans outing beginning of August?
LOL...ahhhh, what frustrating lives we live

>>Thanks again.
Yup
Coz...

John

- - - Updated - - -

Just talked to my contact OS Giken...
Here's what they had to say:

Hey Jim,

If his noise is happening when he is NOT turning, then it is NOT the LSD. Since the LSD is literally open during low torque input as well as on the straights, there shouldn’t be any noises coming from the LSD. If there was a noise, the LSD would be broken and he would really know it by the sound and jarring lockup (pretty much undriveable)

Thanks,
B

 

[1K2GO]

Fingers crossed its a CV. As Coz said, I'd go thru those first and you still might make Spa!

 

[CB72]

A quick update!
I called my friendly Honda dealership today and after exploring all possibilities, he strongly suggested to further investigate a tire related issue?
As we both ride motorbikes he told me that some car tires produce a kind of a ridge when they are ridden hard just like those on powerfull bikes.
This could explain why there is more noise from the rear than the front.
To check this out, I will mount my slicks and go for a ride to determine if there is any change in the noise.
Let's hope I don't meet the cops!

Good news: I didn't get stopped with my slicks...
Not so good news: the noise is still there but I can now define it a little bit better.
The whine is still there but I get the feeling it has always been there?
Now for the grumbling noise.
It happens only when the car is between 30 and 20 km/h and it is more distinct when the car is decelerating versus accelerating?
I've done the test with no brakes applied and the gearbox eitheir in neutral or engaged with the clutch depressed.
At this point, I suspect the noise to come from the rear pads or more precisely from the independent Brembo hand brake pads that might not appreciate the deposits of the PFC 01 rear pads on the disks.
Next test tomorrow without the handbrake pads...

 

[CB72]

Good news: I might have found the source of the grumbling noise...
I dismantled my Brembo parking brakes to inspect the pads closely and discovered that one of the inner pads was down to the metal
It's really stupid because when I changed my rear pads less than 1000 km ago, I looked at the parking pads but saw nothing abnormal.
Needless to say that it's the inner pad that's worn and you can't see it whithout removing the hand brake caliper.
Hard lesson learned ( as usual) but it could have cost me far more than just missing the Spa event:smile:
I will test the car tomorrow to confirm this was the issue!

- - - Updated - - -

I went for a quick ride to determine if there was any change?
The answer is yes and no...
One of the noises has disappeared but there is still a kind of a grumble/booming noise at very low speed?
What's VERY strange is that the OS Giken LSD doesn't make the "marble breaking noise" anymore when I go into a very tight turn like a roundabout???

 

[whitebois]

Loose axle nut- the big 36mm nut you see when you take off your wheel center cap?

 

[CB72]

Nope...
That would have been a relief!

 

[CB72]

I finally decided to tackle my possible gearbox issue.
The plan was to upgrade my spare gearbox to an NSX-R spec differential and then have the gearboxes swapped by the Honda dealer.
As I had already opened an NSX gearbox previously to install an OS Giken differential, I thought it would be easy as long as I had some help to separate the gearbox cases while opening the snapring...
Everything was coming along nicely until I removed the 36 mm sealing bolt at the end of the transmission to reach the famous snap ring.
Guess what ...the snap ring was broken but luckily(?) only in 2 parts.
After quite some effort we managed to split the cases and the internals look perfectly OK.
My car was registered in 1995 and I never thought it could be affected by the famous snap ring failure.
I looked up the serial number and according to the Acura service bulletin, it does fall in the range of the vehicles affected.
What are my options?
1) buy the repair kit as I suppose Honda will not replace it under warranty
or
2) pull the other gearbox out of the car and cannibalize it to use it's transmission housing case
This presupposes that this case is intact but I wonder if it has not suffered the same problem as the Acura service note states that the symptoms are: eitheir the transmission pops out of gear, or you hear a grinding/growling noise on deceleration or acceleration:redface:
It's not exactly the symptoms I observed on my OS Giken equipped gearbox but who knows????
Any advice?

 

[A.S. Motorsport]

I'm fairly sure Honda won't cover the repair, also registration on the car certainly in Europe doesn't say anything about the build date of a car.
I'd need to check but I have ordered new casings from Honda before that would allow you to have two good transmissions.

How does the transmission shift? if you 3-4 are a bit hit and miss that's an indicator as well.

 

[CB72]

I'm fairly sure Honda won't cover the repair, also registration on the car certainly in Europe doesn't say anything about the build date of a car.
I'd need to check but I have ordered new casings from Honda before that would allow you to have two good transmissions.

How does the transmission shift? if you 3-4 are a bit hit and miss that's an indicator as well.

Thanks Adnan, I don't expect Honda to pick up any charge allthough it's a recognized problem in their service note...
In the meantime I opened the 36 mm sealing bolt to determine if I also had a snapped ring on the gearbox currently in the car and ...no problem !
Everything is nicely in place and the bearing turns freely.
At last some good news.
The plan now is to take out the defective gearbox out of the car, pull the top case off that gearbox to install it on my other gearbox and then fit it in the car.
Some work but no expensive parts... so far!

 

[CB72]

Today, I upgraded my " standard" gearbox to NSX R differential specification:smile:
I hope it will give me more satisfaction than the OS Giken differential in terms of daily use?
The upgrade was done following the beautifull video provided here:http://www.nsxprime.com/forum/showthread.php/164794-Convert-nsx-diff-to-nsx-r?highlight=diff
A piece of cake when I realized that the " special" bolts that hold the two halves of the differential only need a standard 12 face socket...
To me it looked like a Torkx socket was needed until I bought one to see that it does not fit
We learn everyday I suppose!

 

[CB72]

I got my NSX back from the Honda dealership today:smile:
We switched the gearboxes in order to install the original one upgraded to NSX R diff specification.
As I mentionned earlier we had to swap the outer case from one gearbox to the other as I discovered that the snapring was broken.
Was this the real cause of the grumbling noise I don't know but the mechanic also told me that the synchromesh for the reverse gear had been smashed?
Since the beginning the reverse gear on my "OS Giken" gearbox had always been difficult to engage with some unmechanical noises.
Buying second hand gearboxes is of course always a gamble.
I'll try to get a few pictures tomorrow.
Next I will pull the OS Giken diff apart to determine if it's still intact?
It was great to drive the NSX home again!

 

[illwillem]

Did it sound like this:

http://youtu.be/78zQd_D7GoE?t=4m8s


I pulled it apart after i got home and found my snapring had exploded. this noise was happening for a week or so before the track event but quieter then got obviously worse on the drive home.

 

[CB72]

Did it sound like this:

http://youtu.be/78zQd_D7GoE?t=4m8s


I pulled it apart after i got home and found my snapring had exploded. this noise was happening for a week or so before the track event but quieter then got obviously worse on the drive home.

In fact I got confused when I wrote the note late last night
The snapring issue happened on the spare gearbox not the one on the car...
So far the only issue we discovered on the "faulty" gearbox ( fitted with the OS Giken diff) is the exploded reverse gear synchro ring???
I listened to your car but as I said to my wife who first heard the noise coming from the rear "hey this is a racing car it's supposed to make all sorts of noises".
The issue is to determine when there is a "new" noise
Here's a picture of the fractured reverse gear synchromesh.

 

[illwillem]

oh, i get it.

I once had a similar type grumbling rumbling skidding noise after a trackday. I pulled over multiple times off the freeway on the drive home and jacked up the car because I was sure i broke and axle or something. The next time I was able to actually get under the car with lights i found this wedged between the axle housing and the heat shield on the passengers side:



it had fallen either the rear beam or the axle support. I was surprised how much terminally bad sounds it was making when driving it. Maybe check between the heat shields?