1991 ford not shifing into overdrive

Asked by Mar 15, 2017 at 12:21 PM about the 1991 Ford LTD Crown Victoria 4 Dr S Sedan

Question type: Maintenance & Repair

1 Answer


Check the vacuum modulator on the transmission. Modulator itself may be leaking or vacuum line to it from engine may be leaking. You can test it with a handheld vacuum pump, it should hold at +/-15 psi. If you see ATF diaphragm is punctured. Engine vacuum is what allows it to shift into higher gear.

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