A downhole adjustable drilling inclination tool 300 comprising: an outer housing comprising a guide pin 308 that extends into an inner diameter; an inner housing 302 comprising a bottom end portion disposed within the outer housing 304; wherein the tool further comprises a compression spring 312 disposed about an outer diameter of the bottom end portion of the inner housing within the outer housing; a piston assembly disposed within the outer housing that is fluidly controlled to move axially along the outer diameter of the bottom end portion of the inner housing so that a rotatable control ring 322 of the piston assembly moves about the guide pin of the outer housing to hold a neutral, straight, or bent position of the piston assembly corresponding to an amount of compression of the compression spring; and a tilt housing 306 partially disposed within the outer housing that includes a bolt plate channel configured to receive a bolt plate pin 332 of the piston assembly that travels to tilt the tilt housing by a tilting mechanism that connects the tilt housing to the outer housing and position the tilt housing in a neutral, straight, or bent position corresponding to the neutral, straight, or bent position of the piston assembly, wherein the downhole adjustable drilling inclination tool is configured to receive a drive shaft within an innermost diameter of the tool. an outer housing comprising a guide pin 308 that extends into an inner diameter; an inner housing 302 comprising a bottom end portion disposed within the outer housing 304; wherein the tool further comprises a compression spring 312 disposed about an outer diameter of the bottom end portion of the inner housing within the outer housing; a piston assembly disposed within the outer housing that is fluidly controlled to move axially along the outer diameter of the bottom end portion of the inner housing so that a rotatable control ring 322 of the piston assembly moves about the guide pin of the outer housing to hold a neutral, straight, or bent position of the piston assembly corresponding to an amount of compression of the compression spring; and a tilt housing 306 partially disposed within the outer housing that includes a bolt plate channel configured to receive a bolt plate pin 332 of the piston assembly that travels to tilt the tilt housing by a tilting mechanism that connects the tilt housing to the outer housing and position the tilt housing in a neutral, straight, or bent position corresponding to the neutral, straight, or bent position of the piston assembly, wherein the downhole adjustable drilling inclination tool is configured to receive a drive shaft within an innermost diameter of the tool. a compression spring 312 disposed about an outer diameter of the bottom end portion of the inner housing within the outer housing; a piston assembly disposed within the outer housing that is fluidly controlled to move axially along the outer diameter of the bottom end portion of the inner housing so that a rotatable control ring 322 of the piston assembly moves about the guide pin of the outer housing to hold a neutral, straight, or bent position of the piston assembly corresponding to an amount of compression of the compression spring; and a tilt housing 306 partially disposed within the outer housing that includes a bolt plate channel configured to receive a bolt plate pin 332 of the piston assembly that travels to tilt the tilt housing by a tilting mechanism that connects the tilt housing to the outer housing and position the tilt housing in a neutral, straight, or bent position corresponding to the neutral, straight, or bent position of the piston assembly, wherein the downhole adjustable drilling inclination tool is configured to receive a drive shaft within an innermost diameter of the tool.