Transmission and Engine Oil Pressure Test Kit, 0-400 PSI

Line pressure is the first number you want before you pull a pan. A slipping 4L60E, a 4L80E that flares on the 1-2, a 6L80 that sets P0868 - all of them come down to whether the pump and the pressure regulator are actually making the pressure the chart calls for. This kit gives you two gauges instead of one: a 0-100 psi / 0-700 kPa gauge for engine oil and low-side work, and a 0-400 psi / 0-2800 kPa gauge for transmission line pressure, which routinely runs past 250 psi in reverse and under full throttle.

Fourteen threaded adapters cover the common line pressure tap and oil gallery threads on domestic and import engines and transmissions, so you are not adapting an adapter. The hose is 72 inches, long enough to route the gauge up to the windshield and tape it in place for a road test or a stall check while somebody else works the throttle. Both gauges have a hanging hook so they sit where you can see them instead of lying on the fender.

Typical use: thread the correct adapter into the line pressure port, connect the high gauge, then record pressure at idle in Park, idle in Drive, idle in Reverse, and at the stall speed the manual specifies. Low pressure across the board points at the pump, a worn regulator bore or a leaking pressure control solenoid; pressure that is correct in Park but drops in a gear points at a circuit leak inside the unit.