[Big Tom]

After this weekends airfield event I'm starting to hear a nasty noise coming from my MT gearbox...
The noise disappears when I press the clutch down or when I rev it a little bit.
The gearbox works perfect, but on the way to the airstrip this morning I noticed that the clutch was slipping a little bit more than it has done before.
I've had some small slippage the last couple of months and I've been planning to get a ACT Clutch.

...and I'm wondering if there's any known MT gearboxes that have failed?
As I understand, this gearbox is the same as in the MT M5 E60, and should therefore be quite oversized and tough?

My workshop will disassemble the gearbox the 12th of September, but it would be interesting to hear your thoughts about this.

Some think it may be a bad clutch throw-out bearing and some think it could be a blown flywheel, but my shop believes it's a blown gearbox...

I'm also out of warranty...

---> So, how many known cases of blown MT gearboxes is there?



.

[issabmw]

I've heard of none.

If the box is the equivalent of the e60, it should be pretty resilient. Keep in mind though, the M5 has 384 lb-ft to work with, and I've heard cases where the M5's box grenaded.

I have doubts that the box is blown, and it does sound like the bearing to me, but I'm no psychic.

[enrita]

sorry to hear man, hopefully nothing too serious.

[R1000K3]

Damn, but it sounds on the video as some part of the clutch that has gone south so it may not be too bad. The dual mass flywheel is also a bit suspected but the gear box should be fine since it operates normally.

[tscdennab]

I wouldn't wait until 12th of september to see what it's all about. You should at least detach the gearbox from the engine to see in what shape is the clutch and flywheel. It doesn't cost more than 100EUR around here.

Another cheaper option is to put the car on a lift and take out the plastic shields from below the car, and then start it and leave it in neutral. You can then hear pretty clearly where the sound comes from.

[dzenno]

It's not your gearbox

[Big Tom]

Originally Posted by dzenno

It's not your gearbox

I hope you're right...

[dzenno]

Look, flywheel is still turning when you disengage the clutch so it's not your flywheel either...you have no trouble making gear changes at all so it can't be your gearbox...only when you engage the clutch do you get the noise...my money is on the pressure plate first, might be disk as well AND the throw out bearing

Hopefully you just resurface that flywheel pop an ACT in there and get back on the road in no time

[jippii ensio]

+1 on what others have said, I think you are fine just getting the new clutch.

Btw. M5 has a lot less torque than any properly tuned N54, so M5 having the same gearbox means nothing.

[FedeM]

I don't think it's gearbox. It seems to be the clutch/flywheel.
My Ford Focus 1.8TDCI (lol) did the same "sound" and it was.

[Gravy]

had the same noise when i put an auto tranny back in a jeep... It was the t converter bolts not evenly tightened... Sounds like it could be anything in between your flywheel and the trans lol... Just drop the tranny and check it out... With that kinda noise it could be as simple as a loose sheild or something but if its something actually grinding you should be able to tell when you drop it. Also check your tranny fluid too.. Heard strange rackets like that when it gets a bit low.

[R1000K3]

Originally Posted by jippii ensio

Btw. M5 has a lot less torque than any properly tuned N54, so M5 having the same gearbox means nothing.

Is this correct? I thought the M5 and a stage 3 335 w/o Nitrous have about the same TQ and the M5 is heavier. I may be wrong though. They should both have about 600 Nm.

[Overboost]

Most likely not your gearbox since the car is driving in every gear.

[hemi to e90]

im going with clutch, the gearbox being gone would be a completely different experience lol

[jippii ensio]

Originally Posted by R1000K3

Is this correct? I thought the M5 and a stage 3 335 w/o Nitrous have about the same TQ and the M5 is heavier. I may be wrong though. They should both have about 600 Nm.

e60 M5 has only 380 lb ft (520Nm) at the crank. At the wheels it is well below 500Nm.

Not much recent dynos out there, but e.g. Mr.5 has dynoed 484 ft lbs at the wheels, i.e. more than 100 lb ft more at the wheels vs M6 at the crank...

[R1000K3]

OK, thanks

[Big Tom]

I removed all the plastic covers and the knocking sound seems to come from the middle and back of the gearbox, not from the clutch/pressure plate/flywheel-area...

That makes me think that the gearbox is blown.
What do you guys think?

[dzenno]

metal carries noises like you wouldn't believe, ask me how I know whatever it is you'll have to drop the tranny and look, no point looking unless you do that...wouldn't waste any more time doing anything else

[Turkeybaster115]

Originally Posted by Big Tom

...and I'm wondering if there's any known MT gearboxes that have failed?
As I understand, this gearbox is the same as in the MT M5 E60, and should therefore be quite oversized and tough?
My workshop will disassemble the gearbox the 12th of September, but it would be interesting to hear your thoughts about this.
Some think it may be a bad clutch throw-out bearing and some think it could be a blown flywheel, but my shop believes it's a blown gearbox...
I'm also out of warranty...
---> So, how many known cases of blown MT gearboxes is there?

Where did you hear this rumor? M5 trans in our E90? That'll be the day. And what's oversized and tough, in our car? The engine? (Maybe, if you have one built between 06-08, cuz then you have forged pistons), the trannies? The turbos? Nah, this car is pretty soft.

As for your question, of course there are cases of blown Manual trannies with these cars. Mr. 5 for example blew his 2nd gear after the power level started getting close to 400whp, and he had an aftermarket clutch. He got his entire trans replaced under warranty. Whats most common though is guys blowing their trans due to money shifting. However, the Manuals do break with extra power, but you can't trust an online forum, because guys love to go online and brag about their Horsepower, but when things break they always typically shy away, out of shame.

[Big Tom]

Originally Posted by dzenno

metal carries noises like you wouldn't believe, ask me how I know

I know, but I could clearly hear that the knocking noise was coming from the middle of the gearbox...
It's harder to hear in the movie than it is live.

[dzenno]

Originally Posted by Turkeybaster115

However, the Manuals do break with extra power, but you can't trust an online forum, because guys love to go online and brag about their Horsepower, but when things break they always typically shy away, out of shame.

...and that's just sad and I know actually quite a few of them never understood what the point was keeping it silent when shit brakes, its like they're ashamed like you say, sad

[tscdennab]

In fact I think it comes from the front of the gearbox (clutch/flywheel area), and it's carried out to the back. I can hear it with a higher frequency at the front, and then it's more muffled in the back.