1. Preparation is Key:
* Safety First: Jack up the truck securely using jack stands, *never* rely solely on a jack. Chock the front wheels. Wear safety glasses and gloves.
* Gather Tools: You'll need a variety of tools, including:
* Socket set (metric and possibly SAE, depending on your truck)
* Wrenches (metric and possibly SAE)
* Torque wrench (essential for proper tightening)
* Drain pan for differential fluid
* Pry bar (possibly)
* Hammer (possibly, a rubber mallet is preferable)
* Seal installer (highly recommended) – prevents damaging the new seal
* New differential seal (ensure it's the correct one for your specific D100's rear axle)
* New differential fluid (the correct type and quantity for your axle – check your owner's manual)
* Shop rags or paper towels
* Consult a Repair Manual: A Haynes or Chilton repair manual specific to your 1989 Dodge D100 is invaluable. It will provide detailed diagrams, torque specifications, and step-by-step instructions tailored to your vehicle. This is your best investment for this job.
* Clean the Work Area: A clean workspace makes the job easier and reduces the risk of contaminating the differential.
2. The Procedure (General Outline – Refer to your repair manual for specifics):
* Drain the Differential Fluid: Locate the drain plug on the differential housing and carefully drain the fluid into your drain pan. Let it drain completely.
* Remove the Axle Flanges: This often involves removing the axle shafts from the differential. This step varies depending on the type of axle (Dana 35, 44, etc.) in your D100. Your repair manual will provide specific instructions and torque specifications for your axle. You'll likely need to support the axle shafts while removing the retaining nuts/bolts.
* Remove the Cover: Remove the differential cover bolts. This may require some force and a pry bar if they're stubborn. Be careful not to damage the cover.
* Remove the Old Seal: Carefully remove the old seal. A seal puller can be helpful, but sometimes a small pry bar can work (use caution to avoid damaging the housing). Clean the seal surface thoroughly, removing any old sealant, debris, or rust.
* Install the New Seal: Use a seal installer to install the new seal, ensuring it's seated properly and evenly. This tool prevents damage to the new seal.
* Reinstall the Cover: Apply a fresh bead of high-quality gasket maker to the differential cover (follow the gasket maker instructions for drying time). Reinstall the cover and torque the bolts to the manufacturer's specifications (found in your repair manual).
* Reinstall the Axle Flanges: Reinstall the axle flanges and tighten the bolts to the correct torque specification.
* Refill with Differential Fluid: Refill the differential with the correct type and amount of fluid (check your repair manual).
* Check for Leaks: After refilling, check for any leaks around the seal and cover.
3. Important Considerations:
* Axle Type: Your 1989 Dodge D100 could have different rear axle types. Knowing the exact type (e.g., Dana 35, Dana 44, Chrysler 7.25, 8.25) is crucial for finding the correct parts and repair information. The VIN plate might offer clues or you may find it stamped on the differential housing.
* Torque Specifications: Using the correct torque values is vital to prevent damage. Your repair manual will list these values for all bolts and nuts.
* Sealant: Use a high-quality gasket maker designed for differential covers.
4. When to Seek Professional Help:
If you're uncomfortable with any aspect of this repair, or if you lack the necessary tools or experience, it's best to take your truck to a qualified mechanic. A botched repair can lead to more serious and expensive damage.
Remember, this is a general guide. Always refer to a repair manual specific to your 1989 Dodge D100 for detailed instructions and torque specifications. This will significantly improve your chances of a successful repair.
