We just got back home from a 10,000 mile trip. During the trip my van (1999 E-350 Superduty) started making a noise. It sounded to me like an idler or tensioner pulley and gradually got louder during the trip. About 1500 miles ago I had time to get it to a shop. The plan was to have the pulleys changed before driving home. The mechanic called back and told me he did not think it was the pulleys. He listened and used a stethoscope and thinks it is the transmission pump. We successfully made it home and now I looking for suggestions of where to start.

You also need to know that last fall the oil cooler located at the oil filter failed and put quarts of oil into the radiator. Following replacement, extensive flushes were required to remove the oil. The hoses were also replaced.

So I am wondering, if it is not the pulleys, could it be the water pump? Could it transfer sound to the transmission area? Would a transmission pump make this kind of noise? We have had no issues with the transmission and the fluid appears normal. We were pulling a camper but the noise was not related to pulling. It did change with RPMs as you would expect with a pulley bearing.

I hope to get it to my shade tree mechanic next week and would appreciate ideas of where to start.

Thanks!