Here's a general outline. Specific details may vary slightly depending on your Bronco's transmission type (C6, E4OD, etc.):
Tools You'll Need:
* New Transmission Fluid: The correct type and amount (consult your owner's manual or a parts store).
* Drain Pan: Large enough to hold several quarts of fluid.
* Socket Wrench and Sockets: Various sizes, likely including a 10mm, 13mm, and potentially others depending on your drain and fill plugs.
* Funnel: For refilling.
* Jack and Jack Stands (or ramps): Essential for safe working conditions. Never work under a vehicle supported only by a jack.
* Wrench for transmission dipstick (if applicable): Some transmissions don't have dipsticks.
* Gloves: To protect your hands.
* Rags or shop towels: For cleaning up spills.
* Torque wrench (recommended): To tighten drain and fill plugs to the correct specification.
Procedure:
1. Safety First: Park your Bronco on a level surface, engage the parking brake, and chock the wheels. Raise the vehicle using a jack and securely support it with jack stands before proceeding.
2. Locate the Drain Plug: The transmission pan is typically located on the bottom of the transmission. The drain plug is usually a bolt on the bottom of the pan.
3. Drain the Fluid: Position the drain pan under the drain plug. Carefully loosen and remove the drain plug, letting the old fluid drain completely. This might take 15-30 minutes.
4. Remove the Transmission Pan (Optional but Recommended): Many mechanics recommend removing the transmission pan to replace the filter and inspect the pan for debris (metal shavings, etc.). This requires removing the pan bolts. Have a pan gasket replacement on hand for reinstalling.
5. Replace the Filter (If Applicable and Removing the Pan): If you removed the pan, replace the transmission filter with a new one.
6. Reinstall the Pan (If Applicable): Carefully clean the pan and mating surface on the transmission and install the new gasket. Reattach the pan bolts. Tighten them evenly and to the proper torque specifications (consult your owner's manual or a repair manual).
7. Reinstall the Drain Plug: Replace the drain plug and tighten it to the manufacturer's specifications (consult your owner's manual or a repair manual). Do not overtighten.
8. Locate the Fill Tube: This is usually on the side of the transmission, sometimes with a dipstick.
9. Refill the Transmission: Using the funnel, slowly add the correct type and amount of transmission fluid. Consult your owner's manual for the correct capacity.
10. Check the Fluid Level (If Applicable): If your transmission has a dipstick, check the fluid level with the engine running and the transmission in park or neutral (warm up the engine first for accurate reading). Add more fluid as needed to reach the proper level. If it doesn't have a dipstick, you'll likely need to refill until it starts to come out of the fill hole. Then, reinstall the fill plug.
11. Lower the Vehicle: Carefully lower the Bronco using the jack.
12. Test Drive: Take your Bronco for a test drive to check for any issues.
Important Considerations:
* Transmission Type: Knowing the exact type of transmission (C6, E4OD, etc.) is crucial for finding the correct fluid type and capacity.
* Fluid Type: Use only the recommended transmission fluid specified in your owner's manual. Using the incorrect fluid can severely damage your transmission.
* Torque Specifications: Tighten the drain and fill plugs to the manufacturer's recommended torque specifications. Overtightening can strip the threads.
* Professional Help: If you are uncomfortable performing this task yourself, it is best to take your Bronco to a qualified mechanic.
This is a general guide. Consult your owner's manual or a repair manual specific to your 1990 Ford Bronco for detailed instructions and torque specifications. Remember to always prioritize safety when working on your vehicle.
