Why you test transmission fluid pressure (the short theory)
- The automatic transmission is a hydraulic machine: oil under pressure is the working fluid that applies clutches and bands to select gears and to transfer torque through the torque converter. The pump makes pressure, a set of valves and solenoids direct that pressure to the correct places, and pistons/clutches convert pressure into mechanical engagement.
- If pressure is too low or erratic the transmission will slip, shift harshly or late, fail to hold gears, overheat, or make internal damage. A pressure test tells you whether the pump, regulator valves, valve body/solenoids, internal leaks or external lines/cooler/filter are failing hydraulically.
- Analogy: think of the transmission as a circulatory system. The pump is the heart, the main line is an artery, the valve body/solenoids are the brain and valves, the clutches are muscles that contract when fluid is sent to them. Low “blood” pressure → weak muscles (slip) or organs (gears) won’t work.

What every component does (brief, clear descriptions)
- Torque converter: bolted to the engine; contains impeller (pump), turbine, stator. Multiplies torque and uses transmission fluid to transfer power. Also has a lock-up clutch that is hydraulically engaged at certain speeds.
- Pump (front pump/gerotor): driven by the torque converter/engine; creates system pressure. It’s the heart of hydraulic pressure.
- Main (line) pressure circuit: the high-pressure output from the pump that feeds the valve body and converter. Measured at the pressure test port.
- Pressure regulator/relief valve: keeps pressure in safe range and directs excess back to the sump. If stuck open → low pressure; stuck closed or blocked → too high pressure.
- Valve body: labyrinth of oil passages and valves (and accumulators) that routes pressure to clutch servo pistons to select gears. Solenoids in electronic systems modulate flow/pressure.
- Shift solenoids / pressure control solenoids: electrically modulated valves under TCM control; change flow paths or pressure according to commands.
- Clutch packs & servo pistons: pistons use hydraulic pressure to apply friction plates (clutches) to engage a gear set.
- Accumulators: dampen pressure shocks and help achieve smooth engagement.
- Transmission filter & pan: filter captures contamination; pan holds fluid. A clogged filter reduces flow and may cause low pressure.
- Cooler & cooler lines: external heat exchanger. Blocked cooler lines can cause back-pressure or high local pressure; leaks here drop system pressure.
- Seals/bushings/shafts/gearset: mechanical internals that can wear and cause internal leakage and pressure loss.

What can go wrong (common failure modes)
- Low fluid level or wrong fluid → low pressure, slipping, overheating.
- Worn pump clearances or damaged gerotor → reduced pump capacity → low pressure.
- Clogged filter or blocked cooler → starved flow → low or erratic pressure.
- Stuck open regulator valve or worn valve body bores → loss of line pressure.
- Worn clutch/friction material or large internal leaks → pressure not building under load (slipping even with correct line pressure).
- Faulty pressure control solenoid or electrical/TCM problems → wrong commanded pressure.
- External leaks (cooler lines, pan gasket) → low level and low pressure.
- Contamination (metal shavings) → sticking valves, ruined solenoids.
- High pressure (less common) from stuck relief → harsh shifting, blown seals.

Tools and parts you need
- Factory service manual or correct pressure spec sheet for your specific Mitsubishi transmission. (Very important: pressure ports and specs differ by transmission.)
- Transmission pressure gauge kit (0–300 psi range) with appropriate adapters for your transmission test ports.
- Hose & fittings specific to your transmission’s pressure test port (do NOT force the wrong adapter).
- Wrenches, screwdrivers, safety glasses, gloves, rags.
- Jackstands or ramps and wheel chocks (do not rely on a jack).
- Catch pan, fresh ATF (correct type), funnel, sealing compound or new port plug.
- Scan tool that can command solenoids/gears (very helpful for electronic transmissions) — optional but recommended.
- Thermometer or OBD temperature reading (to know fluid temperature).

Safety and prep (do this first)
- Work on a level surface. Chock wheels and set parking brake.
- Vehicle must be safely supported (use jackstands or ramps). Take care around a running engine, spinning fan, hot exhaust, and hot transmission.
- Have a fire extinguisher handy.
- Transmission fluid is hot — avoid burns.
- Note: running with pressure gauge installed may leak fluid; keep rags and catch pan under.

General step-by-step pressure test (beginner-friendly, generic; follow your manual for exact ports/specs)
1. Locate the correct pressure test port(s)
- Consult the service manual for your vehicle/transmission. There is usually a threaded port on the case labeled “line pressure” or “test port.” Don’t guess — using the wrong port can cause damage.
2. Warm the transmission
- Start the engine and allow it to reach normal operating temperature (fluid ~80–100 °C / 175–210 °F). Hydraulic pressures are temperature dependent.
- With the vehicle stationary, warm-up by running at idle until the temperature is in spec.
3. Park & secure
- With engine running in Park (or Neutral when specified), set parking brake, chock wheels.
4. Remove the test port plug and install adapter
- Clean around the port to prevent contamination.
- Remove the threaded plug (usually requires a hex or screwdriver).
- Install the proper adapter from your pressure gauge kit. Use the correct thread sealant or washer as specified.
- Attach the pressure gauge and hose securely. Ensure no leaks.
5. Measure basic line pressure (idle)
- With engine idling, read and record the line pressure. Write it down and note temperature.
6. Measure pressure in gears
- With your foot on the brake, move selector to Drive, Reverse, 2, L as required by the service manual, holding each gear for the specified time while noting pressure. Some values change by gear because different clutch circuits are engaged.
- For electronic transmissions you may use a scan tool to command shifts to avoid the vehicle trying to move.
7. Dynamic (applied load) pressure test
- Some tests require increased engine RPM to see how pressure rises with load (e.g., rev to specified RPM while in Drive with brake applied). Follow manual RPM and duration limits — do not overrev or burn the clutch.
8. Record and compare
- Compare readings to factory specifications for each gear and condition. Note whether pressures are within tolerance, low, high, or fluctuating.
9. After-test
- Turn off the engine, remove the gauge and adapter, reinstall port plug with correct torque and sealing. Top up fluid if any was lost.
- Inspect for leaks. Clean up spilled fluid.

How to interpret common results (what it means)
- Pressure at or above spec: hydraulic supply and regulator likely OK; if slipping persists, problem is likely internal (worn clutches) or electrical control.
- Pressure below spec at idle and under load: pump wear, low fluid, clogged filter/cooler, stuck open pressure relief/regulator, external leak.
- Pressure drops when a gear is selected: internal leakage past a clutch pack or valve body bore; worn clutch or piston bore.
- Pressure normal at idle but collapses under load (when accelerating): worn pump or internal leakage; pump can’t maintain flow under demand.
- Pressure high or spikes: relief valve sticking or blocked return; can cause blown seals and harsh engagement.
- Fluctuating or erratic pressure: contamination (sticking valves), faulty solenoids or electrical commands, or TCM issues.

Follow-up checks you should always do when pressure is abnormal
- Check fluid level and condition (color, smell). Burnt smell and dark color = overheating/wear.
- Replace filter and clean pan; inspect magnet for metal debris (silver/bronze flakes = clutch wear; big chunks = serious failure).
- Inspect cooler and lines for blockage or kinking.
- Check for external leaks (pan gasket, cooler lines, torque converter seal).
- Scan for transmission fault codes and check solenoid operation with a scan tool or by commanding them.
- If pump suspected: removing pan and inspecting internals or professional rebuild recommended.
- If valve body suspected (sticking valves): cleaning/rebuilding valve body or replacing solenoids often required.

Common fixes by symptom
- Low pressure due to low fluid/filter: refill with correct ATF and replace filter/pan gasket.
- Low pressure due to clogged cooler: flush or replace cooler/lines.
- Low pressure due to worn pump: pump rebuild or transmission overhaul.
- Pressure collapse in gear: worn clutch packs or leaking piston seals — rebuild required.
- Erratic pressure due to contamination: valve body cleaning or replacement; solenoid replacement.
- Electrical/TCM issues: repair wiring or replace faulty TCM/solenoid.

Practical tips for a beginner
- Always have the factory specs and port locations — do not guess.
- Use a quality gauge and the correct adapter; a poor seal gives false low readings.
- Warm the fluid properly. Cold readings are meaningless.
- If you can, use a scan tool to command shifts and read pressures while keeping the vehicle stationary — safer and more reliable.
- When testing dynamic pressure (revving), keep vehicle restrained with brakes and follow RPM limits to avoid transmission damage.
- Keep a clean work area — contamination is the enemy of hydraulics.

Final notes
- A pressure test tells you whether hydraulic pressure is within design limits; it does not pinpoint every mechanical issue. Use it with fluid/filter inspection, scan tool data, and pan contents analysis.
- Always compare to the exact factory pressure figures for your transmission model. Those values vary by transmission and year — your vehicle’s service manual is the definitive source.

No questions asked — done.
rteeqp73

Galloper / Montero / Pajero 4D56 STRAIGHT PIPE exhaust SOUND ever wondered what a straight pipe (no muffler) 4D56 sounds like? well here it is.

Part 1: Fill-up mineral water bottle & place it snug on the (cold) radiator, start engine...

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