Grinding sound after gearbox oil and filter change

[btjtaylor]

Hi all

I have an S6 c5 but I think the gearbox is the same as the RS6 (or very similar) so I'm posting here as there's a lot more activity,

It had a gearbox rebuild approx 180k it's on 220 now so wanted to do a bit of preventative maintenance,

I performed a full gearbox filter change and following the instructions included to the letter (drain, install filter, fill it up until it drips out, start engine, fill some more, cycle gears, check level, done)

When I started the car back up there was an awful noise:
https://youtu.be/SJJMg01d2Kc

Took it for a VERY short drive to the end of the road and the gearbox seemed to work ok but the noise was horrendous so I came back

Anyone had this before?

Thanks in advaxe

Any help greatly appreciated.

[Human Joist]

Did you check the two filters to confirm they are the same. If memory serves there are two and they differ

[btjtaylor]

Just had the gearbox sump back off again and compared old and new filters, i cant see any real difference between them,

[Capt Ric]

Have a look on this and other forums, I think I read something recently about having to trim a pipe on the filter in some cases.
Sorry don't have time to look for it now.
Hope it helps. Good luck.

[Mɐʇʇ]

See my post here with the correct measurements.

[btjtaylor]

Thanks for that , will measure the filters I have when I can next work on the car

From doing a bit of research looking at videos/photos of the box off the car (https://www.youtube.com/watch?v=A-IrMzeB74s was very useful) the noise is coming from the torque converter/pump area.

If the pump is running dry due to oil pickup issues it could explain the noise. I just hope its not decided to fail. On the plus side it looks as if I could get away with replacing the pump or torque converter without specialist tools/knowledge like I would likely need if there was a problem inside the box itself.

[Mɐʇʇ]

They do make a lot of noise not just if "starved", but also if the oil is heavily aerated. Just in case, consider popping it back on the ramps and topping it off according to the procedure again - certainly when I replaced the box on mine, the first fill was sucked up pretty quick and it all ended up a bit frothy & noisy until I let it settle. Also it is important the car is level (at least by eyeball). I use 2 sets of ramps, front and rear (Obvs I have to jack it to get it up on the rears - but I prefer ramps to stands when possible). Also worth noting there is a min temp (30C) as well as a max, which is sometimes missed on the procedure.

If it does need to come out & if you do it yourself, I think my post elsewhere here gives you a download for the service manual (the C5 S6 is in there too, IIRC). And having had the box out of mine, myself, on stands in the garage - it's not "that" bad as long as you're patient and methodological. No turbos, intercoolers and such like will only make it easier! There is a trick to getting the box & TC off easily - the trick being to following the service book precisely rather than thinking "I know what I'm doing" and making it harder - as I did.

[btjtaylor]

Just did the refill (used a new filter too, measured the pipe it was definitely 20mm) and... Success! Gearbox sounds quiet and working beautifully.. even better than before the change!

I think you were spot on about the oil being aerated... On the second fill up I used a "syringe" type pump to put the oil in. Was incredibly slow doing 200ml at a time but got there eventually. Before I used a hand pump and I reckon it aerated the oil as it was going in and caused an air lock.

Unfortunately I wasted near enough £100 on fluids and a filter but it's better than a new box!!

*Breathes a deep sigh of relief*

[Human Joist]

Pleased for you mate. That’s on the list for mine this year as well

[Mɐʇʇ]

Cor! I bet 200ml at a time tried your patience!
FWIW, I don't think it's so much the filling device as it is that when you first start up with a new filter & clean sump, it's easy for the pump to suck in some air.

So just fill it up to the brim, fire the motor up and fill it up as per the spec. Then with sump plug in, motor off for half an hour, the fire it up again and top it off according to the procedure.
IMVHO of course - but that works for me.

[steve2003rs6]

Pleased I read this. Mine will be done this year so I now know what to look for.

[Mɐʇʇ]

Clearly that's the difference between the S6 and the RS6. I don't think anyone breathes a sigh of relief with the RS. But the smiles make it all worth it.

*Breathes a deep sigh of relief*

[btjtaylor]

Just returned from a 600 mile trip with no problems at all, thanks for the advice everyone,

Ordered a fuel pressure regulator to try to sort a niggling warm start problem .. I posted a thread about that a while back but needed to get my arse in gear to sort it ..