The manual came from factory with a "dual mass flywheel" (DMF). Click
here for the Wiki page on it. You'll have to ignore the "damage was caused by going solid flywheel" bullshit because it doesn't apply and I suspect the author of that section or the referenced information was talking about using vastly inferior clutch/flywheel combos.
The main problem (that the Wiki page doesn't even touch) isn't that parts of the DMF become unreliable. If you know how clutches work, you'll know where the problem is (and for those that don't know, read on).
The clutch itself is normally clamped against the back of the flywheel by the pressure plate. When you depress the clutch, the pressure plate relaxes its hold and the clutch slips against the flywheel. This disengages the engine from the gearbox allowing gearchanges or, through fine application of the pressure ("riding the clutch"), a partial transfer of power through the clutch.
It's this last aspect that's the actual problem. When you're reversing, or manouvering something heavy (boat up a ramp, caravan up a driveway) you tend to slip the clutch a fair bit. Fine? Not with a DMF.
The act of allowing the clutch to slip creates heat in the pressure plate, the clutch and the flywheel. Because the DMF's face is (necessarily) quite thin, it can't hold or transfer as much heat as a thicker (single mass) flywheel. It then overheats, the clutch overheats and the pressure plate overheats. Suddenly the pressure plate can't hold the clutch against the flywheel any more and the car stops.
If you have a manual D40 with a DMF fitted and it's giving you grief (gently driven, or minimal "riding", won't cause problems) then replacing it with an Exedy HD system will not only resolve the problem but it will fix it for good.
The wiki page doesn't do a great job of explaining why car makers fit DMFs either. It's actually rather simple. In any combustion engine, one cylinder is going to be pushing its piston down during its combustion phase, and the others won't be. Some of the others might be starting their compression stroke. As the piston reaches the bottom of its travel, the crankshaft slows down a fraction as the other cylinder reaches max compression. When that cylinder ignites, the crankshaft speeds up again. This slow-fast-slow-fast is absorbed by the springs in the DMF. If you have a SMF you might notice a little extra vibration while driving, especially at low revs.
So why do it? The car makers need to make the diesel engined vehicles (which have a larger speed differential in crankshaft rotation from combustion -> compression) more attractive to the mums and dads. It has to drive like a normal sedan, it has to be smooth like a normal sedan. Their attempts have actually worked - there are heaps of utes on the road nowadays!
