Hi, I’m looking for some help/advice please, if someone has the time?

Car:

Mazda 6 2.2 150ps Sport Nav Diesel

6 Speed Manual Transmission.

42K miles.

A few weeks ago I noticed a faint noise while driving, it sounded like a chinook helicopter was in my engine, but quite, muffled. The sound come from the engine area, and is noticeable through the footwell. Listening with the windows open while driving I can’t hear the noise due to road noise.

The noise is relative to road speed, not engine revs. If I rev the engine, still at idle, or driving with clutch depressed, it sounds flawless. Smooth, normal.

As I pull away and begin to drive the noise begins. The frequency of the thud/bang/knock is regular, and sounds like a bolt in the tyre (it isn’t that), in terms of revolutions etc. It’s most noticeable between 10 and 35 mph on smooth tarmac. Above that it’s harder to hear, presumable due to road noise, or the frequency increases to create a continuous sound that becomes indistinguishable from car noise.

I’ve begun to explore the front end of the car, and I’m trying to figure out what it is - as it seems very likely to related to the transmission, not the block.

I have:

Checked Tyres
Checked Wheels
Checked Rotors and calipers
Visually inspected drive shafts

Those all seem fine, visually etc.

Ive jacked it up, wiggled the wheel at 3-9 and 12-6 and seems good.

While jacked, only on one side, with the other front end wheel on the ground, I’ve rotated the wheel. This seems to generate the noise I’m hearing. I did the same to the other side, and again, I can subtly hear the noise. It sounds in board, not near the wheels at all.

I then jacked the whole front end, and started the engine. I let the car go up through the gears, as the transmission spins the front end faster the noise comes on, loud and obvious from outside and inside. Like a regular muted chinook noise. If I listen, it’s very much coming from the gearbox area..

I intend to jack the whole front end again, and hold one wheel at a time, and let the other wheel come up to speed in 3rd, independently each side, to rule out shafts and wheel bearings each side. I suspect it isn’t these due to hearing the noise both sides while the other side is locked.

I haven’t yet inspected under the tray, but I will tomorrow. I’m guessing (as it makes the noise whether the clutch is in our out) that it’s gearbox or diff related?

Any thoughts greatly appreciated!

 

Use a wooden stick touching the suspected area and your own ear (like an stethoscope) on that stick to pinpoint where the noise is coming from. Let us know what was the problem, good luck

 

LOL that a new one..

This may actually be a better sound detaching DIY tool..(for various reason all having to do with how sound travels through and object and what the object is made up of)












Easiest that any DIY can make with common "stuff and tools in any garage!

 

Whatever suits your needs, as long as conducts vibrations, if it does work, it does work :-)
Old timers used just a long screwdriver, with the tip on the area you wanted to listen, and with the ear on the screwdriver's handle.
The one with the screw and the screwdrivers is also new to me, lol. I should try that.

 

Those are all good ideas, thank you!

I did jack the front end up in the end. With both front wheels off the ground.

I started the engine, and had somone hold one wheel steady, I then went up through the gears to 5th. The engine spun the whole transition on the other side, and I heard the noise clearly inside the car and outside. A single rotation quiet banging noise relative to rotation speed. Far more noticeable from 3rd upward, but present all through the gears I’m sure.

I then did the same on the other wheel, and let the other side of the transmission engage. Same noise, same characteristics.

I’m no specialist, but this would surely rule out wheel bearings, drive shafts and so forth?

When I get under and listen it’s pretty obviously coming from the bell housing and gearbox side of the engine.

The gears change fine, and the engine sounds perfect when revved in neutral and in gear, so surely this must be a rotational noise from either the differential or some parts of the gearbox that remain in direction rotation with road speed right? The noise doesn’t sound at all like it’s linked to the speeds of the flywheel, engaged clutch or gearbox input shaft.

Has anyone had a gearbox make a noise like this on a Mazda 6? Or indeed other car? What could be knocking or banging inside there?!

 

Ya well you are no audiophile that's for sure. And if you were really alert you would have seen that the picture with the driver having the tube and fastener allows for a better way to get into areas without having your head so close to it. Helps prevent brain damage.

 

Couple things ..
It was a good attempt.... but..

without loading the drive wheels most sounds to the untrained ear will sound ok. Also, your method of locating while would or might narrow it down somewhat sound has a funny way of traveling in the total different location then you would think. So again, to the untrained ear locating noises sounds and even vibration is inconclusive
Asking this to other DIY if they had these sounds and vibration I would be responding exactly the same thing.

I go on test drive with customers frequently before we write the service order and what I hear and feel going on is many times very different from what the customers states.
Your best advice is finding a shop that is willing to go on a test drive with you before you sign the service agreement. This will at least reduce the diagnostic time to find or identify your concern.

 

Okay so a gearbox garage confirmed it is teeth (probably) in the gearbox. Which is what I thought.

I'm going to change it myself - does anyone know the differences between the models that attach to the 2.2 diesel?

Mine is EB FB D6020

I have also seen EE FB 6050

I have seen also D6010 and D6040

All are 6 speed manual rated between years 2013 - 2020 etc

Any specialist gearbox advice out there folks? Thanks so far for all your help :-)

This is my code. EB FB D6020

 

Just curious as some of us invested time to respond to your need and question to help you I ask... How did they "confirm" the teeth and then you say"probably" ??? lol
So basically guessing right?? lol

Confirm broken teeth:

Sound
Can feel the broken teeth by manual manipulating the input or output shaft
Finding large gear, synchro or other large metal parts by daring the fluid
Removing the transmission and dissembling it for inspection

or
GUESSUING

 

Hey!
Thanks for the reply They didn't confirm 100%, just told me what they think it is, which considering I only asked for a free diagnostics is all I'll get.

You are right, a listening tool would have helped to confirm the location precisely! Better than my head under the car, and recording the noises on my phone at different places! At some point, I'll need to change parts to fix the noise, and there's so little else that this could be. Even if it's pressure plate or flywheel, it's still box off. And seeing as it isn't related to engine speed I think we have it.

I was confident in my approach though, in terms of holding each wheel while up on stands. If either side is held tight, one at a time, and the noise prevails, and isn't related to engine revolving, but to transmission rotation, then I think we've got our target.

I stripped out the under tray, inspected the whole area, and changed transmission fluid weeks ago for inspection. It didn't reveal anything. I was expecting perhaps a shimmer to the oil, but it was good. Again, if anyone can think of any last minute ideas if this isn't the gearbox I'm all ears, given the details provided above?

I've bought a second hand gearbox as I can't afford a new one £3,100 + VAT.. I have paid £200 for one on about 60K miles.

I matched the gearbox part number with the local Mazda dealership. I'll change the gearbox in about a week and a half and report back!