That is the water pump pulley.
Pulley.
The belt on a 2000 Ram uses a spring loaded tensioner pulley. It self tightens.
Gas engine, it is the part the fan is screwed onto. Diesel, it is just to the passenger side nd down from the fan pulley.
To change the fan belt pulley on a 1996 Dodge Ram 1500 with a 318 engine, first disconnect the negative battery cable for safety. Next, remove the serpentine belt by releasing the tension from the serpentine belt tensioner. Once the belt is off, unbolt the fan belt pulley from the water pump or alternator, depending on which pulley you are replacing, and replace it with the new one. Finally, reattach the serpentine belt and reconnect the battery cable.
That pulley is part of the water pump. The water pump has failed and needs replaced.
You need a 36 mm wrench and a spanner to hold the pulley. Turn counter clockwise to loosen.
loosen the idler pulley and then remove the belt. then you remove the fan shroud i believe its like 4 bolts, then you remove the fan. after that you can remove the water pump.
You need two special tools, A 36mm wrench and a spanner to hold the pulley still. While holding pulley yo use 36mm wrench and a hammer to turn fan nut counter clockwise.
12 valve it is on the front of the engine, above the crankshaft pulley. 24 valve it is behind the starter, in the side of the block.
You can remove the old serpentine belt on your 2004 Dodge Ram by loosening the tensioner pulley. Put the new serpentine belt on and tighten it with the tensioner pulley.
I have a 1995 Dodge Ram 1500 and it has a counter-clockwise rotation; or a left turn rotation.
Check clutch fan