1. Check the Vehicle's Data Plate (or Sticker):
* Location: This sticker is usually located on the driver's side doorjamb or the glovebox.
* Information: It may list the rear axle ratio (e.g., 3.55, 3.92, 4.10, 4.56). This isn't the *exact* differential model, but it's a crucial piece of information. Different ratios indicate different differentials.
2. Inspect the Differential Housing:
* Location: The differential housing is located in the rear of the truck. You'll need to get under the vehicle to see it.
* Casting Numbers: Look for numbers cast into the metal of the differential housing itself. These numbers are usually located on a relatively flat surface. Use these numbers to cross-reference with parts catalogs or online databases. A picture of these numbers will be helpful if you seek online assistance.
3. Look at the Differential Tag (if still present):
* Location: Sometimes a tag is attached to the differential housing. This tag might have codes or numbers that identify the differential. This is less common on older vehicles.
4. Consult Repair Manuals or Online Resources:
* Repair Manuals: A factory service manual for your specific year, make, and model of Dodge Ram will have details on the differentials used.
* Online Resources: Websites like the Dodge Ram forums, parts catalogs (e.g., RockAuto), or online vehicle databases might help identify the differential based on your VIN or other information.
Important Considerations:
* Front and Rear Differentials: Your 4x4 Dodge Ram has both a front and rear differential. The methods above will primarily help identify the *rear* differential, as it's usually easier to access. Identifying the front differential typically requires more involved inspection.
* Variations: Dodge Rams came with a variety of differential options depending on the trim level, engine size, and optional equipment.
* VIN: Providing your Vehicle Identification Number (VIN) will significantly increase the accuracy of any online searches for your specific differential.
By combining information from the data plate, physical inspection, and online resources, you should be able to identify your 1998 Dodge Ram 4x4's differential. Remember safety first – if you aren't comfortable working under your vehicle, take it to a mechanic for inspection.
