What oil is used in a rockwell rear end?

The type of oil used in a Rockwell rear end depends on the specific Rockwell rear end model and the year it was manufactured. There's no single answer. Rockwell produced a wide variety of axles for different applications (trucks, construction equipment, etc.) over many years.

To determine the correct oil, you must consult:

* The owner's manual: This is the most reliable source.

* The data plate on the differential: This plate often lists specifications, including recommended lubricant.

* A Rockwell parts catalog: This can be found online or through a heavy-duty truck parts supplier. You'll need the model and serial number of your axle.

The oil will likely be a heavy-duty gear oil, possibly a hypoid gear oil, with a viscosity grade (like 80W-90, 85W-140, etc.) specified for the operating temperature range. Using the wrong oil can severely damage the rear end. Don't guess; find the correct specification.