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Gearbox explosion :-(



  E46 M3
Driving along yesterday night and gearbox went bang, oil dumped out, rapid deceleration, pulled straight off the road and that was that. Game over.

I eventually got it home at about 1am with the help of a friend and the spent all day today wondering what’s gone wrong with it.

We (potentially stupidly) towed the thing home for maybe 3 miles at about 10mph - me sat there with the clutch in and the front end sounding like a bag of marbles.

Tonight I’ve managed to get the car up to have a looksie at what’s happened and In the plastic undertray I found 6 roller bearings that were all a bit chewed up. Poked my finger in the gap where the flywheel is and fished out another. I could also see one of the flywheel teeth has some minor wear on it (presumably where it’s whacked one of the aforementioned rollers).

Anyone car to hazard a guess what’s happened and how much damage has been done? I’m already scouting for a new gearbox, I’ll get a new clutch whilst I’m at it, but my main concern is that something might have buggered up in the engine that has literally just had the belts done 50 miles ago (it fired up absolutely fine so hoping it’ll be ok).

Thoughts welcome :)
 

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  SG9 Forester STi
Oof not good! I can't comment on potential engine damage but if you're located anywhere near Essex then I know a company who refurbs the gearboxes. I had mine done on my old clio and it was good piece of mind to know that everything was fresh.
 
  E46 M3
That’s the taper roller bearings for the mainshaft that’s let go. Most likely at the diff end. They always fail.
I imagine it’s been rumbling for a while now and finally let go.

Thought something like that would be the case. Weird thing is the only warning / first sound of something weird was the day before when I started hearing a very faint whine, but it was so faint I didn’t think too much of it. Then literally next time The car was driven, kaboom. Before then all seemed fine (other than the usual poor 2 to 3 gear change at high rpm).

Chances of engine being damaged?
 

NorthloopCup

ClioSport Moderator
Thought something like that would be the case. Weird thing is the only warning / first sound of something weird was the day before when I started hearing a very faint whine, but it was so faint I didn’t think too much of it. Then literally next time The car was driven, kaboom. Before then all seemed fine (other than the usual poor 2 to 3 gear change at high rpm).

Chances of engine being damaged?
Cut the crank sensor bracket off your box and mount it on the engine. Start it and see if it runs ok, but I doubt it’ll have damaged it tbf.
 
  E46 M3
good to hear. everything is still connected up so I will wait until I've figured how to get the box off before trying what you suggest :)
 


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