So my car has been making this noise while reversing. Link to the video of the noise.

It's a 1997, 940, B230fk, M90.

What do you guys think this is?

https://www.youtube.com/watch?v=23HdviLd-ek

I am yet to completely confirm this. But I'm very confident saying that in this situation this noise is due to low fluid level on the transmission. It was pointed out by someone on volvoforumsuk that it could be the reverse idle shaft making the noise, because it was above the fluid level (or rather the fluid was bellow).
THis was made worse by the fact that I?ve been parking the car downhill recently, so the already low fluid level was pushed to the front of the transmission.
This theory is further validated by both the fact that after driving for a while the car would stop making the noise (because it got lubricated during driving) and by me changing the direction of the car at the parking spot, meaning facing up, forcing the oil to the rear and therefore submerging the rev. idle shaft which caused the car to not make this noise anymore.

I'm yet to check the level because I'll just order the oil first. But I'm pretty sure that's it. Quite a weird one I guess.

So if anyone has a weird accute squeaking noise only in reverse driving uphill that goes away after driving a bit, check the tranny fluid level.

Hi,

Oh boy I sure do wish you luck in the oil level being the cause!

Since I know so little about the M90 or the 900 series as a matter of fact I went out to see if I could get an illustration of one.

https://forums.turbobricks.com/showthread.php?t=94325

I ran into that above and found it very interesting about the type of clutch used to drive the M90.
It's Interesting, in that, it's a different design than any Chevy or 240's
If you read enough of the articles on this site you will get what I mean about being different.
There is a discussion about the worthiness of it all too!

After reading it I will stick with my original idea that the "hollow" sounds with the hint of "ringing" is not a counter shaft bearing running dry on oil sound.
A main driveshaft support bearing yes, but then, when their dry it's more of a high pitched shrill. Same for a tensioner bearing on the engines timing belt.

On most all manual gears boxes the reversing lay shaft, or a countershaft to some folks, is found in the bottom of a gear box.
It is always submerged in oil and out of the way so to speak because it use so infrequently.
That is except in the motion pictures (Fast &Furious) where they go as fast in one reverse gear, as others go in all their forward gears!
Anyway,
This is so the main throughput gears are up high to keep the driving output shaft up higher in the driveline design.
The oil tracks itself up to the top of the gear case by the way of the gear teeth and splashing about for the most part.
If a A pump was use, this will add expense and can be "parasitic" draw on the final output power.
This went on for years and worked against the acceptance of automatic transmissions.
So, consequently you don't find many manuals provided with powered lubrication.

Today, that has all changed and now look out, here comes the electric motors with variable everything! (::--)

Good luck and make sure you get the right oil for it!

Phil

I get what you're saying, and as soon as the oil arrives, I'll know whether or not low level is the reason.
But if you were correct, how would you explain that the car stopped making noise when I started parking it the other way around? I've driven it 2 times now and I got zero noise.
In the M90 the reverse idle shaft is out of the way but not all the way at the bottom, but a bit raised. That, coupled with the way the car is parked, could be the explanation. Anyway, I'll know within the next few days for sure.

Hi,

I can understand where you are coming from and having things, like those sounds changing and wanting an explanation.
I’m no guru but I’m in the mix of life just like you! (:-)

I can say without a doubt the changes are happening because you are there!
You are interacting with the car or otherwise we would not be engaged in trying to figure this out.
The next thing to consider is the cars environment and age of all the variations that go on with that. It’s a cause and affect relationship.

Temperature and humidity play a key role with things.
Even barometric pressures, as subtle as they move, effect our planets surface. It’s the inside of our planet and stuff way outside it.
It’s a living physics experiment that’s has some constants but at the same time surprises we have yet to comprehend.

Your car was built by those born on earth, expect some unknowns!
I’m not familiar with the car and of course, any type “mass changing” experiment unique to a M90’s dual clutch?
Like I said it’s an interesting type of clutch and transmission you have!
Unknown condition too!

I will say one thing that’s it’s most likely something called “Friction Plate Dust” build up.
Just like brake pads squeal and it develops on some cars while others have no issues what so ever!
Is it the pads, the rotors or a drivers habit and/or locality?
You got me?

If you park the car in the same place but you never turn it around and to get out differently?
That’s an Interesting slant on things. (:-)
What do you do, back up in a circle? It, Might explain, half of the time? (:)

I can only guess, something is changing, but it leads me to believe there’s always a variable going on!
I have no direct answer except it’s still drivable.
It will resolve itself but who knows how?

Tell us what oil you have to put in this transmission.
I’m experimenting with a brand called Fuchs on my two M47’s. Less expensive than OEM and authorized handling markups. It’s a synthetic thermal oil just like Amarin states.
So far no issue within them getting more noisy but I know the oil, in itself, won’t fix what is mechanically not right.
Wrong oil, from a PO’s Indy, hurt one really bad! I have it pulled out.

Volvo doesn’t make their oil.
They buy from vendors just like doctors buy drugs from certified drug peddlers!
Who knows if a car or a human body is going to have a bad reaction to an ingredient in something, before they use it? Stupid drug commercials!

Volvo now has three different part numbers. Upgrades or what?
What about Dexron’s past and GM’s woes?
Go figure, that what I’m doing, is a “very low pay grade” experiment. (:-)

I could suggest you blow the clutch out with dry compressed air or even use a very cleaning light solvent combination. Short of an inspection and that’s a half circle, In, itself.
If your oil is low, It had to go someplace!
Like the links show from Turbobricks, we just don’t know a lot.

Brake calipers can benefit from a blow job but a investigation but a correction is best.
Being they are brakes and all!

Imagine back when parking brakes were on the mounted right on driveline shaft behind the transmission.
Even stagecoaches had wheel brakes.
Around and around we go!
If you slow down you might get run over, today!


Phil

Be sure to order the correct oil for your manual transmission. The M90 uses fully synthetic oil. Don't use ATF. ATF are used in M46/M47 gearboxes. I provide some photo and links below.




Turbobricks has updated oil listing for the M90:
https://forums.turbobricks.com/showthread.php?t=94325


In short your M90 uses oil #1161745, #1161645 or #1161423. In case its hard to get proper Volvo oil, Skandix offers equivalent oil from LiquiMoly, similar to #1161745:
https://www.skandix.de/en/spare-parts/accessories/chemicals-consumables/oil/transmission-oil-manual-transmission-1-l-75w-80/1058457/


Take care of your precious M90. You have a very nice car there!


Amarin

I don’t know anything about the M90 trans but could the OD have an internal clutch that slips when the thrust is reversed? Seems I’ve heard of that possibility in other model gearboxes.

I made a new test. To put the car at that specific clutch point at which it makes the noise while the park brake was still on, and I discovered the car only makes the noise if it moves. I tried all pedal positions and no matter what, unless the car started moving a little bit, the car was silent. Basically, what I thought was a specific clutch point, was just the point at which the car starts moving.

Can you guys help me interpret this? If it was clutch related, wouldn't the car still make the noise while not moving? Because the gear is engaged, the car is making the force to move, it's just not moving because the handbrake is on!
Right now I'm thinking this is most likely a movement related thing and not necessarily clutch. Because basically the car seems to make the noise exactly when it starts moving very slowly and stops making it as soon as it picks up speed. But then again, I'm pretty sure it only happens if reverse is engaged, meaning if I just let the car drop a bit backwards, it wont happens. If it was brake related it probably would, right?

I've seen your latest video: https://www.youtube.com/watch?v=F9-776vCjaI

I think its parking brake shoes. I had similar noise before (while reverse).

Use your handphone in audio recording mode. Tape/stick it on the body near the rear tires. Or if you have earphones with mic then tape/stick the mic instead. Reverse the car slowly. And confirm where the noise came from.

Amarin.

I hear you. But why would that stop making noise after driving the car for some time? And I've also tried just pushing the handbrake really strong and drive riht after and it doesn't make the sound again. Only happens when the car is cold, basically.

Why it happens when the car is cold? Temperature related maybe? I suspect its due to some dirty parts inside parking brake assembly. In my case, I dismantled the rear caliper and disc out, sprayed lots of brake cleaner to clear old brake dust, greased some sliding points and the noise is gone after installing it all back. Do both sides.

Amarin.

Dragging park brake shoe? Detached heat shield dropped down on drive shaft? Normally those would make a scuffing noise in both directions, but maybe worse in reverse. Just wild guesses as my speakers are pretty bad for listening. Maybe put the rear axle (not the frame) safely up on stands or blocks and see if you can duplicate it.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

If it was the park brake, wouldn't it make the noise again if I push the brake and reverse the car again? I've tried that. And the car seems to go silent or almost until I park it for some time.
Some people on Volvo Forums UK mentioned it doesn't sound like brake stuff. I know it's hard to distinguish especially in a video.

But at the same time, it was so sudden and the lack of other tranny/clutch related symptoms makes me think it must be something less serious. But I probaly should at least check the transmission fluid level. It was changed 32000km ago, but might be just low.

Hi,

I’m not a 940 person but off hand I would have to say it’s a driveshaft support bearing gone super dry! The bearing is really rusty and sure as heck doesn’t like being turned backwards.
I know it sounds like a reach but roller bearings usually screech long before this going forward.
If it is the bearing or the supporting member that supports everything under there then there is something rubbing.
Sounds loud enough to be sheet metal in this case?
There should be a shiny spot someplace with this scenario?
Should have to be around the driveshafts output end from the transmission. That would be the tail shaft bearing or bushing in older automatic 240s. It’s inside the rear housing.
I don’t know for a fact but they can be replaced from the outside or I would hopefully think so!
I only own one 240 with an automatic transmission.


I don’t understand why you are doing all the turning of the steering wheel but the should add drag to the front end of the car or load through the drive shaft.
If the pitch changes with the turning of the wheel or only when they are in extreme lock to lock position then that puts the noise related to the front end of the car.
If the wheel bearings are super loose then the wheels are shifting and the brakes discs are raising hell with the calipers and possibly a dust/water shield.

Without a directional source, I cannot draw up any other visual explanations in my mind.
Maybe a video from outside the car while you are backing up and the camera and microphone 🎙 going along outside with the car would be more helpful to other 900 owners.

Phil

Now that you mentioned the driveshaft, I'm wondering if what sems to be a direct correlation with the clutch is not just that when the pedal is fully released the car is already at a speed at which it doesn't squeal.

Please 940 whisperers, help me! I'm so confused!

Hi,

This goes to show you what I know of the 900 series.
I didn’t know a M90 was a manual shift car! I was thinking only an automatic from the sounds of the shifter operating. I guess I thought I was convincing myself that it was an automatic. (:)

So now that you have a clutch in the car, that makes a big difference!

That sounds very well could be a bad clutch assembly as it’s slipping and chattering.
Why only in reverse does seem very odd though?

Does a chirping sound happen when letting the clutch out when going forward as well?
It will be shorter in duration and more likely to happen only when the clutch is the coldest.
Did you do all that backing up first thing!
After driving the car does it become less or stop all together in reverse after all things are up to operating temperature?

Shame you don’t have someone listen outside the car as that particular sound does have the tendency to emanate from everywhere with its volume.
It should sound like it’s from underneath the car.

A Car Talk show provided a checking procedure and that’s was to put the car up against a tree or solid wall.
Then, with the car in second gear or higher and let the engine idle or slightly above and push the object.
If the engine doesn’t stall the clutch is shot!
This might also create the noise.

I would suggest using a thick blanket though and spread the load to your bumper surface with a flat piece of wood and not a tree! As they are usually round and not very big in diameter! (:)


Phil

Honestly, not sure about the clutch question. It sure happens a lot when I'm releasing the pedal. I think it's more of a releasing issue. But that's one thing to test later or tomorrow.

I'll also have the wife be outside to see if she can spot the source of the sound. Or order a cheap usb microphone to place under the car in different locations.

I did back up first thing because the spot I park at as a tree righ in front, so I always have to reverse. But I've tested that it doesn't do it in first gear even if the first thing I do is go forward. But I'll test that again.

After driving, it basically stops. I've just made another video. Better sound: https://www.youtube.com/watch?v=F9-776vCjaI

I just test drove it for about 5 minutes and the sound was almost if not entirely gone.

Yep!
I think your have a glazed clutch disc and possibly some hot spots on both the pressure plate and the flywheel surfaces.

How many miles or kilometers on this clutch or is it an original?
The original clutches on these cars go far longer than replacements due to all the things being new.

Oil seals and usage take their tolls over time. Do you have oil leakage underneath?
And of course “time” always passes on its “deeds” to everything. (:)
All we can do is train ourselves to live with it or around it, as best we can!
Nothing gets out of life alive and unscathed or your not living!

What you want to do is refrain from ever feathering the clutch pedal during operation.
You mentioned doing that in the last video.
Get your foot off the pedal as soon as you can after any take offs.

It’s best to do not idle for long periods of time with the pedal in either as this prematurely wears on the throw out bearing.
Yours is still of if you do not hear anything while depressing the clutch pedal.
Leaving the foot on the pedal can cause slippages and premature wearing of the disc but more importantly slick spots on all four surfaces that make up the friction clutch pack.

The good news you have a warning, that it has worn, but you will still get more mileage or kilometers on the car until it won’t stall the engine against a load or pull itself when passing another vehicle in a hurry!

Edit
Now Dave Stevens might be the 900 man worth following up on in your hunt for a noise!
Phil

My car has 495000km and the current clutch kit is OEM changed at the dealership and has 82500km. The lack of other symptoms and the parts being faily new, makes me think it might be something else. I'll check oil level first and rake related stuff.

Hi Phill,

Thx for the help.

I've went and made a few more tests and filmed with my camera that has better audio. Was alone so don't have sound from exterior.

The car only makes the squeak at clutch point in reverse. When the pedal is fully depressed the car doesn't make any sound. The noise only happens in reverse and seems to be worse when I start the car or it has been parked for a while (a while might be as little as 1h or so, because it has happened to me after going to the supermarket).

The wheel turning was just because that road isn't too straight. No other reason. I've also tested it going straight and I get the same noise.

I will investigate the driveshaft support bearing possibility.