For normal service, periodic fluid level checks are not required. When the vehicle is serviced for other reasons the exterior surfaces of the axle assembly should be inspected. If gear oil leakage is suspected inspect the fluid level CHASSIS FLUIDS AND LUBRICANTS. This inspection should be made with the vehicle in a level position.
To check the axle fluid, park the vehicle on a level surface. Take a piece of wire (or zip tie) and make a 90 degree bend two inches from the end of the wire. Insert the wire into the fill plug hole and use it like a dipstick. Remove the wire and measure from the 90 degree bend to the oil level.
For the 2500 (Non-Power Wagon) axles, the fluid level should be 4/5 in ± 1/4 in (20.3 mm ± 6.4 mm) below the fill hole for the rear axle and it should be 1/4 in ± 1/4 in (6.4 mm ± 6.4 mm) below the fill hole on the front axle.
For the 2500 Power Wagon and all 3500 model axles, the fluid level should be 1/4 in ± 1/4 in (6.4 mm ± 6.4 mm) below the fill hole on the 9.25 in front, 11.5 in rear axle, and 12.0 in rear axle.