Need some advice from the experts...

[FrenchAudi]

I have a similar noise on my 1994 Alfa, which also has an in-line engine and gearbox, with a clutch arrangement much like VAG, but without a DMF.

I bought the car 4 years ago with 50,000 miles, little used by an aged owner. It has now done about 65,000 miles.

I noticed the noise shortly after I bought the car and decided it could be the release bearing, but more likely the input shaft bearing, as, like yours, the noise stopped when the clutch was depressed.

The clutch failed early in 2015. I got around to repairing it in January this year, and found the release bearing had partly seized and chewed through most of the diaphragm fingers, probably due to rust forming in the bearing while unused for so long before I bought it.

I replaced the complete clutch and release bearing, and also checked the input shaft for oil leaks and play, but it seemed OK. I noticed some slight wear marks on the top and bottom of the spigot which guides the release bearing, so I refitted this in its support so the wear marks are now at the sides.

The noise is still exactly the same as before I replaced the clutchand still stops when the clutch is depressed.

It could be the input shaft bearing, but could also be the release bearing rattling on its spigot, the release lever rattling against the gearbox housing, or even the input shaft splines rattling in the pressure plate.

The noise has been the same for 4 years now, I can only hear it when the car is stationary, and I'm not going to do anything about it unless it gets a lot worse.

[MiniMental]

Think it's definitely input shaft noise. I don't understand why it's so amplified under engine braking in 3rd, 2nd and 1st when moving down through the gears to a stop... The giveaway for me is that when idling on the drive it's noisy till I press the pedal, then it takes a second for clutch to stop spinning and noise goes. If I let it up to bite point in neutral, noise is instantly back again. If I repeat the same whilst in gear, I feel the clutch bite but there's no noise. Silent. Whe it's noisy its like bad wheel bearing noise with a slight rattle...

Any input welcome. Am I looking at another box given the effort needed to get it off or is it an easy fix once off?

Cheers
Aidan

[FrenchAudi]

I agree it is most probably input shaft noise. But it could possibly be caused by backlash between a pair of the constant mesh gears when they are unloaded, or even damage to these.

I'm going to check the gearbox oil level, just in case that is a factor.

The Alfa has a two-part input shaft with a splined coupling between the parts, so that is another possibility for me, but your input shaft should be one piece if it is similar to the corresponding Audi item.

If so, it is possible to replace the input shaft bearing without dismantling the box, but this requires a couple of special tools. See 5-Speed Manual Gearbox 012/01W Front-wheel Drive

[FrenchAudi]

It may not be much use to you, but I think I have found the cause of my rattling noise as being from backlash in the gearbox due to uneven idle speed.

The engine is idling at about 750 rpm, a bit lumpy with some hestation, but when I increase the idle to just under 1000 rpm the noise stops completely.

As the idle speed is controlled by a module which varies the volume of air through a throttle bypass I shall have to clean this up or replace it, but at least I know I don't have a terminal engine problem.

I suggest your noise is due to the input shaft front bearing, as you think, or damage to one or more gears. As I posted above, you may be able to change the bearing without stripping the box.

[MiniMental]

Yeah I'm gonna have a look. In for four new tyres on Monday, coupled with clutch and DMF that's me all spent out this month lol. It's makes no difference with engine speed on mine. Only stops when I press clutch as standstill. Mine being diesel, idle is controlled by fuel not air, I do have a 'notchy' idle when cold, but only for 10 seconds or so.

Thanks for the suggestions though, it is much apprecatied. I think I'm gonna source a box off eBay and swap the entire thing when I get chance.

[FrenchAudi]

I'm not sure I'd trust a secondhand box, unless I were sure it came off a very low mileage accident write-off.

I think, if possible, I'd get an exchange 'box and return mine after fitting it, or buy a secondhand one and have that rebuilt.

All depending on how much work you want to do fitting 'boxes, and the costs involved.

[MiniMental]

Seen a few 67k milers on eBay for around £150 mark with 3 months guarantee. I think I'm unlucky tbh, from what I've seen and heard, vw boxes are usually pretty bullet proof. Second hand box isn't gonna be any worse than mine lol. Not hard to change. Some trim a jack and a few bolts.. Lol. We'll see. Car is getting on and needs loads doing. A recon box would likely push the boundaries of what it's worth...

In need of:
Exhaust
Shocks
Rear brakes
Four tyres (Monday)
Headlight polishing
Extensive Stone chip repairs
New rear bumper trim (struggling)
All new door locks
Front wheel bearings
Cambelt
Water pump
Gear gaiter
Gearbox (evidently)

Nothing drastic, all cheap and easy enough but not all at once lol

[MiniMental]

Oh, starter motor and rear wiper motor... Starter motor sticks out when starting for a second or so and I snapped the washer tube off inside wiper spindle on the back.... Wouldn't mind, but I did it at the end of refurbish the whole wiper motor Assy as in to tight to buy another. Works good as new now except the washer lol.

It's a labour of love but I love the car too much to give up... Fantastic to drive and at the age where it's modern and economical yet easy to work on at home, not just a bundle of electrics which needs a garage all the time.... Think I'll have it for life. Lol.

[MiniMental]