Fix It

Start the engine and let the 1993 DeVille warm up. On some GM cars, including the Cadillac line, once the engine has warmed up, the gearshift may be operable. Also, check to ensure the brake pedal is working by pressing down on it. If warming up the car doesnt resolve the problem, go on to the next step.

Manually trip the brake shift interlock solenoid. Start the car. Lift the rubber panel cover under the ashtray and open the under-dash compartment door.

Shine a flashlight into the under-dash compartment and look for an orange lever tab. Push orange lever tab toward the hood of the DeVille to override the automatic lock manually. Listen for a click that indicates the solenoid has been released.

Depress the brake pedal again and attempt to shift the Cadillac into gear.

Position a jack under the front of your Jeep and raise it off the ground. Position a set of jack stands under the front axle housing, then lower the Jeep until it is resting securely on the stands.

Slide under the passengers side of the Jeep and locate the vacuum shifter or actuator on the axle housing. It sits behind a small metal skid plate or guard. Remove the two bolts from the skid plate with a socket and ratchet, then remove the skid plate and set it aside.

Locate the two black vacuum lines on the end of the shifter. Pull the lines off the shifter and lay them aside. The lines are different sizes so there is no concern about mixing them up later.

Remove the four 10-mm bolts from the four corners of the actuator or shifter using a socket and ratchet. Set the bolts aside for reuse later.

Pry the shifter assembly loose from the axle housing with a stiff putty knife, then lift the assembly off the housing. Scrape any remaining gasket material off the housing and place a clean rag in the opening until you are ready to reassemble it to keep dirt and water out of the axle.