I’m actually from Europe but I hope I can also get a little help here. I’m aware that this particular problem might be hard to guess without proper diagnosis or replacement of some parts, I’m not asking for itbut I’d rather like to hear out some opinions or advices what to check.
I’ve recently bought a Renault Laguna 3 GT equipped with a 6 speed PK4008 gearbox and a 2.0 turbocharged engine tuned to ~235hp and 370Nm connected to the gearbox via duall mass clutch. It’s FWD and the gearbox is on the left so the right driveshaft is long and has an intermediate bearing in the middle.
Since the beginning I’ve heard a small whining noise on fourth gear, it wasn’t really that disturbing so I just ignored it. However I think after swapping the wheels for winter (one size smaller aluminium rims) the noise got more intensive. You can hear the noise on this video: https://www.youtube.com/watch?v=jbtSwhJkBFA it’s not mine and not even my car, but it’s mostly the same.
I talked with some people and most of them say it’s the gearbox, although some people who had similar problems in other cars and they even replaced their gearboxes and still had the noise or it was just more quiet (including the author of the video above!). At first I was also sure it’s the gearbox because I thought it only happens on second and fourth gear, but eventually after some testing I concluded that it’s actually related to speed and somewhat a little in gears too. I also met one person who had similar problems and everyone told him it’s the gearbox (even guys who do gearboxes) and eventually he ended up swapping the driveshaft and got rid of the problem, although he doesn’t remember some details anymore and can’t assure me he had identical symptoms. I havent found any identical problems regarding my particular gearbox online, there were some cases of 5th and 6th gear bearings going bad in diesel engines, but in my case these gears are flawless.
Let me describe in steps what happens and what does not happen, I hope someone can draw some conclusions from this and at least tell me if the syptoms are more valid for intermediate bearing or gearbox bearings/differential:
1. Noise begins at 30km/h (first/second gear), goes for a little and then disappears until ~60km/h. Then as I keep accelerating it gets more audible until around 100km/h where it disappears or gets muffled by the engine.
2. When in these speed ranges, the noise is audible on any gear (third, fifth, sixth) although it is kinda loudest when in 4th gear and driving around 70-100km/h, when on third it is similar but the engine is louder, on fifth or six the noise is not as loud but still can hear it in example when slowing down.
3. When pressing and letting go of the gas, the noise kinda disappears for a second and appears again (it sounds a bit weird)
4. When rolling in gear without gas the noise is the same
5. Pressing clutch or putting neutral makes the sound a lot quieter, but it’s still there and can be heard
6. During neutral when the sound is quieter, TRYING to push the gear shifter into gear (third or fourth for example) actually causes the sound to appear before even it’s in gear, the sound appears when I feel resistance on the shifter
7. Pressing brakes or turning the wheel doesn’t affect the noise
8. A few times I observed temporary vibrations on the steering wheel when slowing down around 100km/h which I think could also be the driveshaft starting to fail since I cannot reproduce it
9. I think swapping the wheels for smaller made the noise louder, although I’ll need to try putting old wheels back to make sure
10. Gearbox works fine, not a single problem with gear change observed
11. The oil in gearbox was allegedly changed by previous owner, I thought maybe some low oil level could cause that and I’m going to change it again anyway although I’m holding off since I’ll need to do it anyway if changing the driveshaft
Can’t think of anything else. Anyway, I watched lots of videos about bearings/driveshaft bearings and for example this video: https://youtu.be/5q7Dg_hyX8M?t=82 shows very similar sound coming from the driveshaft bearing (atlhough completely different driveshaft but still..).
I really wish it’s not the gearbox so I’m searching for clues as I don’t want to go out replacing pricey parts not knowing if they’re bad. Cost of an OEM driveshaft is similar to having the gearbox renovated and there’s like only one cheap replacement that I have no idea about. If I’m spending that amount of money it better be fixed 😀
Reading these 11 points above, what does it sound more likely to be? Is it possible that pressing the clutch makes the intermediate bearing whine less despite the wheels spinning at the same speed? At the same time, if it was the differential would the noise drop that much when pressing clutch or putting in neutral?
Is there any cheap way to actually tell if it’s one or another? I’m gonna put the car up and spin the wheels and try to locate it with a stethoscope, but I know the dude who replaced his driveshaft did the same and mechanics told him it’s the gearbox for 90%.
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