Abstract: An automatic transmission line pressure regulator includes a first body for installation in a valve bore distant from a line pressure valve and having a threaded bore passing therethrough, a threaded adjuster axially engaged in the threaded bore and rotationally adjustable with respect to the first body, a second body for installation in the valve bore and engagement with the threaded adjuster and a spring for installation between and engagement with the second body and the line pressure valve. Rotation of the threaded adjuster with respect to the first body alters an axial position of the adjuster, the second body and a first end of the spring, thereby altering a pre-load on the spring to alter a resistive force against movement of the line pressure valve caused by line pressure, and thusly, regulates line pressure.