1. Sourcing the Posi-Traction Rear End:
* Finding the right unit: You need a rear end assembly from a similar year S10 (or possibly other GM vehicles with compatible axles) that already has a limited-slip differential. The gear ratio should ideally match your current rear end's ratio (check your current axle code on the axle housing) to avoid speedometer inaccuracies and potential drivetrain issues. Used parts are common and usually more affordable than new ones.
* Identifying Posi-traction: Look for markings on the differential cover or casting itself that indicate a limited-slip differential. Common terms include "G80" or similar GM codes.
* Verification: Before purchase, try to confirm it's functioning correctly. This is difficult if buying used, but a reputable seller will give you some indication.
2. Tools and Equipment:
You'll need a wide array of tools including:
* Jack and jack stands: Essential for safely lifting the truck.
* Wheel chocks: For added safety.
* Socket set (metric): Various sizes will be needed.
* Wrenches (metric): Including open-end, box-end, and possibly adjustable.
* Torque wrench: Crucial for proper tightening of bolts.
* Impact wrench (optional but recommended): Makes removing and installing axle nuts much easier.
* Transmission jack (recommended): Helps support the transmission while separating the driveshaft.
* Driveshaft support: Keeps the driveshaft from dangling and potentially getting damaged.
* Gear oil: Appropriate weight for your new rear end.
* Differential carrier bearing tool (possibly): May be necessary depending on the differential design.
3. The Process:
1. Safety First: Secure the vehicle on jack stands, and engage the parking brake. Chock the wheels. Disconnect the battery's negative terminal.
2. Remove the Wheels and Tires: Remove the tires and wheels from the rear axle.
3. Disconnect Driveshaft: Separate the driveshaft from the rear end. This often involves unbolting the driveshaft from the differential flange. Support the driveshaft with a support bar to prevent damage.
4. Drain the Differential: Drain the gear oil from the rear end.
5. Remove the Rear Axle: This involves removing bolts securing the axle to the vehicle's frame. This may require removing brake lines and other components. Precise steps vary slightly depending on the year and model. Consult a repair manual specific to your 1991 S10.
6. Install the Posi-Traction Rear End: This is the reverse of the removal process. Make sure the new unit is installed correctly.
7. Reconnect the Driveshaft: Secure the driveshaft back to the new rear end.
8. Refill Differential: Fill the differential with the correct type and amount of gear oil. Check the owner's manual or a repair manual for the specific oil type and quantity for your axle ratio.
9. Reconnect Brakes and other components: Reconnect any brake lines, electrical connectors, and other components you removed during the axle removal.
10. Reinstall Wheels and Tires: Reinstall the wheels and tires.
11. Lower the Vehicle: Carefully lower the vehicle back to the ground.
12. Test Drive: After driving a short distance, check for any leaks or unusual noises.
4. Important Considerations:
* Repair Manual: A factory service manual specific to your 1991 S10 is highly recommended. This will provide detailed instructions and torque specifications.
* Professional Help: This is a complex job. If you're not comfortable with automotive repair, it's best to have a qualified mechanic perform this task. Incorrect installation can lead to serious damage to your vehicle.
* Axle Codes: Carefully note the axle codes on your current axle to ensure you get a replacement with the same gear ratio for proper speedometer and odometer readings.
This process is a significant undertaking. Improper installation could lead to damage to your truck or even injury. A shop manual and possibly professional help are strongly advised.
