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Q: My Expedition vibrates a lot when stopped at a slope

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Every time I park my car on a slope (my garage driveway for example) it starts vibrating. Two days ago, I was turning right over a mild slope and suddenly I heard a huge sound coming out from the engine and the car almost came to a stop. But thereafter it ran fine, like nothing happened. The dealership recommended I replace the engine ($8000)!! They replaced selenoids, cam shaft and a cam phaser. It drives OK now but I'm not sure for how long. The other weird thing I noticed after replacing the selenoids was that may car stopped heating up. I drive it over two hours and when I get home the engine is kinda cool, isn't that odd? Why cars act up when on a slope? It doesn't seem like an electrical issue but maybe hydraulic. Can you help?

My car has 109000 miles.
My car has an automatic transmission.

Hello and thank you for your question. This symptom is not related to the engine but rather the transmission. If you drive the vehicle around and the engine runs just fine, then either the engine oil is low, causing the engine to be starved of oil on a slope, or the transmission bearings inside the transmission are worn out, causing the transmission to kick out of gear when at an angle. Usually the AODE transmissions, which is what your vehicle is equipped with, has an issue with the input shaft being out of alignment when it gets worn causing a mass leak in the torque converter to the input shaft. This makes the pump lose pressure and causes the clutch to release inside the transmission. I recommend hooking up a pressure tester to the transmission at the front of the transmission next to the oil cooler lines and monitor the pressure as you drive the vehicle. When going on a slope, if the pressure drops, then you need to remove the transmission and replace the input shaft seals. If you need assistance with your transmission, then seek out a professional technician from YourMechanic who can come to your home or office to diagnose your transmission problem and make the necessary repairs.

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