Won't backup it locks the wheels won't go forward wheels also locks up

Suburban parked facing down what would cause reverse and drive to lockup

And struggling wheels to lockup?

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Hi,

Check the level of the transmission fluid is OK

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If the parking brake isn't engaged on hills or at least the front wheels turned into the curb to stop vehicle movement, the mechanical parking pawl isn't designed to hold a vehicle from moving forward or backward. In a very heavy suv, the mechanism may bend from not using the parking brake. Repairs may be necessary depending on damage.

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