I'll keep this short and sweet. The R50 Mini Cooper is often maligned for the Midlands 5-speed gearbox. The internet makes it seem like they are a time bomb waiting to go off. Are they really that bad? There seem to be enough running around with higher mileage.
If you try to shift them they blow up.
If it's on the internets you know it's true. Just like Porsche IMS bearing failure
What do I know, I never had a Mini and am drunk
They are that bad, I've seen several die before 100k. I've disassembled two of them post-failure and found the pinion bearings failed. The drain/fill plugs come with magnets, check them for metal debris as that often shows up some time before failure.
Is this like the internet lore that states every WRX trans will explode, or it it based in reality?
There was a successful class action suit on these transmissions. Do they all explode? ....No,but the number that do is higher than normal. There are several reasons they fail, not just a single fatal flaw. Synchros give up prematurely, seals go and the gearlube leaks out, and there's a third one that escapes me right now.
I agree with the comments above, and have personal experience as I had one fail at 90K in my 2003 R50. I took it apart and it was the carrier bearings, not the pinion bearings, in mine. There is very limited parts availability for these--you can get "rebuild kits" for about $600-700 which include bearings, seals, maybe synchros, but not individual parts. You can also get "remanufactured" units from MINI or some aftermarket suppliers. There aren't any really good options in my opinion.
I ended up swapping to a 6 speed Getrag unit from a R53 (Cooper S). It's a decent swap, but it requires the transaxle, the half shafts, the starter, flywheel/clutch, and a few other bits from the R53, so the costs add up if you aren't careful.
Sounds to me like it is one of the few things that makes a MINI seem like a real Mini. Metal shavings on your magnetic drain plug should be looked at as a feature, not a flaw. Consider it a quaint throwback to an earlier age.
Why not just step up to the R53. There isn't that big of a price gap these days, and unlike most of the internet opinions, my '06 has been trouble free for the 3 years I have owned it. It's a great car.
T.J. wrote: Sounds to me like it is one of the few things that makes a MINI seem like a real Mini. Metal shavings on your magnetic drain plug should be looked at as a feature, not a flaw. Consider it a quaint throwback to an earlier age.
Funny, I was reading this thread and flashing back to the Rover Minis. The classic Mini gearbox relies on a number of shims for proper clearances. After a while, Rover just stopped making a range of shims and stuck the same size in every gearbox. Which was wrong more often than it was right. So the new owner had a gearbox rebuild in fairly short order.
Did mine last winter 
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