This 3.6L does have a tensioner. What is an overrunning clutch? I think i know based on what i felt when i spun the alt looking for noises but im not 100%. And no the one i took off dont seem bad in terms of slop or noise when spinning but it was not charging for sure.
when the engine speed decreases but the alternator is spinning, while its activated and charging, would not want to slow down as quickly as the belt is. Those shock loads are traditionally taken by the automatic tensioner in, say, a square. THe overrunning clutches is when the belt is now slowing down but the alternator is still spinnin, it freewheels in the opposite direction of rotation so it doesnt put the wear on the belt/forces on the other pulleys, etc
my 2006 hyundai has one on the alternator i replaced. Its the funny looking pulley you showed
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the clutch can fail, its a mechanical device that wears, some are built better than others, but you can replace them too. If it fails in the sense your alternator pulley spins, but it doesnt turn the actual shaft, that would probably come on gradual with "slipping" and low rpm would have low output with high rpm barely cutting the cheese. They can fail like bearing seize and then no turning happens.
notice the funny aspects of the pulley compared to a normal one?
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heres a little synopsis from gates website. They have their place, and you could even put them on an old square 10si if you wanted, and frankly wouldnt be a bad idea for a AD or CS conversion with a serp belt because the brackets can sometimes be pushed past their ability from the forces and the shocks, because they are heavier, turn more mass, and when outputing at their higher ability, sudden slowing would be far surpassed even original CS130 trucks because they didnt have to withstand that stuff. Leading to misalignment and then reduced belt life, bearing life, noise, etc you know the drill. But its not as critical in a large engine even with not the best brackets. Its really noticeable when you factor in modern pulley ratios and small engines with high output alternators, the smaller engines I think usually have a smaller crank pulley or the ratio between accessory is different because of where power is made and with regards to smooth operation, and a lot of vehicles a ac compressor that is fixed displacement that cycles frequently and pulleys that dont overrun would be freqently felt in the cabin and of course there is a drive to have less and less transmitted NVH above all that even, so an AD244 being turned by a 2.2l 4 cylinder at high rpm, high output in a small crossover isnt just gonna accept slowing down without a fight lol
if i fix my park avenue im gonna look at putting one on my ad237 when i rebuild it it(bearing is wearign out, original alt tho! 1999) because with the supercharger, its easy to get belt slip and the excessive amount of idler pulleys to accomodate the 2nd serpentine belt and tensioner would prob appreciate not facing as much resistance and shocks when slowiing down, sicne the alternator is toward the higher amp side and is also at the outer edge of the belt routing, with a fair amount of wrap, I would prob extend the life of other devices. And its accessible on that engine, unlike most newer vehicles. If I need to service the clutch it can be done with a 15 mm socket and bar and the special tools to put them on without having to dismount the unit... but thats my car, not everyone would see as many gains in their application I think