I have a JD 5105 with approx 700 hrs. When idling after warm up, I have noticed a fairly loud "rattling, ratchet" noise that appears to be coming from somewhere on the left side of the engine. However, with just a light load on the engine (i.e. engaging the power steering by slightly turning the wheel) the noise tends to disappear. I unsuccessfully tried the "stethoscope" approach and tried to isolate the noise but had no luck. I released the belt tension on the alternator but it had no effect either. I also examined the water pump but there is no whining or leaks at the pump. Could this be a bad drive gear to the injector pump? How would I check this without taking off the cover?