I've got a knock that started all of a sudden. I'm not sure what it is and I don't want to drive my truck until it stops. It seems to be located behind and down from the tensioner pulley, it almost sounds like its coming from inside the casing itself. Any ideas what it might be?

 

What were you doing (how were you driving) when the knocking started?? sounds like a rod knocking.....

 

Just some in town driving, nothing over 30 to 35 and no fast acceleration or anything, just taking it easy. I thought it might be a rod, but I'm not for sure. I took the belt off and started it for just a few seconds just to make sure it was any of the bearings attached to the belt. Its not, it continued to knock without the belt on.