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.
SYS.OK|MANUAL.DBβ LIVE
HOMESERVICE MANUALSFORD1991AEROSTAR VAN CARGO EXTENDED, 4.0 X, AWDREPAIR AND DIAGNOSISTRANSMISSIONAUTOMATIC TRANSOVERHAUL - A4LDTESTINGSHIFT SPEED TESTROAD TEST
1991 Ford Aerostar Van Cargo Extended, 4.0 X, AWD
Road Test
1991 Ford Aerostar Van Cargo Extended, 4.0 X, AWDSECTION Road Test
This test will determine if electronics, governor and shift control valves are functioning properly. Converter lock-up is difficult to detect. A vacuum gauge and tachometer should be used to determine lock-up speeds.
- Check light throttle upshift with transmission in Overdrive (with approximately 10 in. Hg). Transmission should start in 1st gear and shift automatically into and through each gear, then lock converter at predetermined speeds. See appropriate SHIFT SPEEDS table.
- Converter clutch lock-up only occurs after Overdrive gear is obtained. With transmission in "D", all upshifts are automatic (except for overdrive). With transmission selector in 2nd gear, transmission will only operate in 2nd gear.
- When travelling over 45 MPH with transmission in 3rd gear, transmission should downshift into 2nd gear when selector lever is manually shifted from "D" to 1st gear. This will determine if governor pressure and shift control valves are functioning properly.
- When traveling at approximately 45 MPH in Overdrive or "D" and transmission is manually shifted into 1st gear, transmission should shift into 2nd gear. When speed drops below 30 MPH, transmission will downshift into 1st gear.
- During coastdown from approximately 45 MPH with transmission in Overdrive and throttle closed, as vehicle speed drops, downshift sequence is:
- Converter Electronically Unlocks (When Accelerator Pedal Is Released)
- Downshift From Overdrive-To-3rd
- Downshift From 3rd-To-2nd
- Downshift From 2nd-To-1st
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.