Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSMERCURY1989GRAND MARQUIS GSREPAIR AND DIAGNOSIS (SINGLE PAGE)TRANSMISSIONAUTOMATIC TRANSOVERHAUL - AOD
1989 Mercury Grand Marquis GS
Overhaul - AOD
1989 Mercury Grand Marquis GSSECTION Overhaul - AOD
- Application
- Identification
- Description
- Lubrication & Adjustments
- On-Vehicle Service
- Trouble Shooting
- Notes
- Symptoms
- Slow Initial Engagement
- Rough Initial Engagement
- Delayed Or No Forward Engagement, Reverse Okay
- Delayed Or No Reverse Engagement, Forward Okay
- Delayed Or No Reverse Engagement And/Or No Engine Braking In Manual Low
- No Engine Braking In Manual 2nd
- Forward Engagement Slips, Shudders Or Chatters On Engagement
- Reverse Engagement Slips, Shudders Or Chatters On Engagement
- Starts Up In 2nd Or 3rd
- Incorrect Shift Points, Harsh Or No Upshift
- Early, Mushy, Soft Or Slipping Upshift
- Erratic Shifts
- No Forced Downshift
- Transmission Overheats
- Transmission Clunk Or Squawk During Upshift
- Transmission Noisy (Valve Resonance)
- Harsh Initial Engagement Into Drive
- Delayed Reverse Engagement
- Slips & Chatters When Hot, Delayed Drive & Reverse
- No Forward After A Stop
- No Reverse
- No 2nd, 4th Or Reverse
- No 2nd Or 4th, Reverse Okay
- No 3-4 Upshift
- No 3rd Or 4th
- 2-3 Squawk
- Clacking Noise Or Squawk, Intermediate Buck On Deceleration
- 3-4 Slip
- Neutral Condition On 3-4 Upshift
- Bucking On Deceleration & Kills Engine When Stopping
- Chatters Or Bucks On Acceleration Or Deceleration In 4th Gear
- No 3-4 Upshift Until 50 MPH, Or Until Accelerator Pedal Is Released Slightly
- Harsh 4-3 Or 4-2 Downshift
- Bearing Whine In All Gear Positions Except 3rd & 4th
- Clutch & Band Application Chart
- Testing
- Road Test
- Control Pressure Test
- Control Pressure Test Results
- Direct Clutch Pressure Test
- Shift Speed Specifications (Mph)
- Governor Check
- Stall Speed Test
- Stall Speed Test Results
- Air Pressure Tests
- Flushing Converter
- Leak Test
- End Play Check
- Stator One-Way Clutch Check
- Damper & Hub Assembly
- Stator Interference Check
- Removal & Installation
- Disassembly
- Component Disassembly & Reassembly
- Reassembly
- Torque Specifications
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.