To find the correct amount, you must:
1. Identify your axle ratio: This is usually found on a sticker on the differential itself (often on the driver's side), or in your owner's manual. It will be a number like 3.73, 4.10, etc.
2. Check your owner's manual: This is the *best* source of information. It will specify the correct capacity for your specific axle ratio and differential type.
3. Consult a Ford repair manual: A repair manual (like a Haynes or Chilton manual) will also provide this information, often with diagrams showing the fill and check points.
4. Go to a reputable parts store: If you know your axle ratio, a parts store employee might be able to look it up for you in their system or cross-reference it with their manuals. However, always double-check the information provided.
Do not simply fill the differentials to a certain line. Many differentials don't have a dipstick. The correct procedure usually involves filling until the oil comes out of the fill hole. This is crucial to avoid overfilling, which can damage the differential.
In short: Don't guess. Consult your owner's manual or a repair manual for the precise amount needed for *your* 2004 Ford Explorer.
