The engine came out of same vehicle? guessing it is a grand cherokee.? The rear drive plate / flywheel is same part number 99 and 2004.as is the oil pump drive, the sensors are a different part number, but that is probably because the connectors changed.was this a 50,000 mile original engine or 50,000 miles on a rebuilt engine? move the oil pump drive 1 tooth and see what happens, see how it runs. cylinder #1 is the very front.