Here's a breakdown of the general steps involved:
1. Preparation:
* Safety First: Disconnect the negative battery terminal. Use jack stands to securely support the vehicle. Wear safety glasses and gloves.
* Gather Tools and Parts: You'll need a variety of tools including jack stands, socket sets (metric and possibly SAE), wrenches, a torque wrench, a drain pan, a differential carrier bearing separator, a gear oil pump, a wheel puller (if needed), and possibly a press for installing bearings. You'll also need the replacement differential, gasket, seals, and gear oil appropriate for your differential.
* Consult a Repair Manual: A Haynes or Chilton manual will provide detailed diagrams and torque specifications specific to your Astro. This is crucial for success.
2. Removal:
* Drain the Differential: Locate the drain plug on the differential housing and carefully drain the gear oil into a suitable container.
* Disconnect Driveshafts: Disconnect the driveshafts from the differential. This typically involves removing bolts and possibly using a driveshaft separator tool.
* Disconnect Brake Lines (if applicable): Depending on the design, brake lines may need to be disconnected. If so, be prepared to catch any spilled fluid and properly bleed the brakes afterward.
* Remove the Differential: This involves removing bolts securing the differential to the axle housing. There will likely be multiple bolts and nuts. This step can be physically demanding. You may need to use a pry bar (carefully!) to help break the differential loose.
* Remove the Differential Carrier Bearing (if applicable): This step might involve using a differential carrier bearing separator tool.
3. Installation:
* Clean and Inspect: Thoroughly clean the differential housing and the new differential. Inspect the axle housing for damage.
* Install New Seals and Gaskets: Install new seals and gaskets on the new differential as per the repair manual.
* Install the Differential: Carefully install the new differential into the axle housing, ensuring proper alignment. This may require some force.
* Install Carrier Bearing (if applicable): Properly install the carrier bearing, using the correct tools and ensuring proper alignment.
* Reconnect Driveshafts: Reconnect the driveshafts, ensuring they are properly seated and secured.
* Reconnect Brake Lines (if applicable): Reconnect brake lines if necessary and bleed the brakes thoroughly.
* Fill with Gear Oil: Fill the differential with the correct type and amount of gear oil, as specified in your repair manual. Use a gear oil pump to avoid spills.
* Check Fluid Level: Check the fluid level using the fill plug.
4. Final Steps:
* Torque Specifications: Tighten all bolts and nuts to the correct torque specifications as indicated in your repair manual. Using the wrong torque can damage components.
* Test Drive: Carefully test drive the vehicle to check for leaks, noises, and proper operation.
Important Considerations:
* Professional Help: If you are not comfortable with this type of repair, it's strongly recommended to take your vehicle to a qualified mechanic. This is a complex repair with the potential for significant damage if not done correctly.
* Specialty Tools: You will likely need some specialized tools for this repair, and renting them might be more cost-effective than buying them.
* Safety: Always prioritize safety. Use jack stands, wear appropriate safety gear, and follow all safety precautions outlined in your repair manual.
This is a simplified overview. Always consult a repair manual specific to your 1988 Chevy Astro van before attempting this repair. Failure to do so could result in damage to your vehicle or personal injury.
