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Transmission Slippage

Problem

Solution

Low oil levelCheck and add oil
Wrong oil gradeCheck oil grade
Weak or broken pressure regulating valve springDo Transmission System Pressure Test
Transmission pump suction screen restrictedRemove and clean screen
Low transmission pump flow due to worn pumpDo Transmission Pump Flow Test
Transmission control valve or gasket leakageRemove valve and inspect gaskets
Clutch cut-off valve stickingRemove and inspect clutch cut-off valve
Restricted modulation orifice housing orificesRemove control valve housing and check for restrictions in valve and valve
Excessive transmission element leakageDo Transmission Element Leakage Test Using System Pressure
Worn clutch disksRepair transmission

Unit Will Not Move

Problem

Solution

Low or no transmission pressureSee Transmission Pressure is low (all gears) or Transmission Pressure is low (one or two gears)
Service brakes will not releaseDo Brake Pedal Operational Check. Do Service and Park Brake System Drag Checks
Park brake applied or parkswitch misadjustedAdjust park brake switch
Stuck control valve spoolCheck shift linkage operation. Disconnect shift linkage from control valve spool and check linkage movement.
Failed torque converterDo Torque Converter Stall Test. If engine pulldown is normal, torque converter is good
Broken shafts or gearsDrain transmission to determine if large pieces of metal contamination are present
Broken drive shaftsInspect drive shafts and universal joints for external damage. Repair
Broken ring or pinion gearIf drive shafts rotate with transmission in gear but unit does not move, a differential failure is indicated. Repair

Transmission Pressure Is Low (All Gears)

Problem

Solution

Low oil levelCheck transmission oil level and refill if necessary
Switch failureVerify transmission system pressure. Do Transmission System Pressure Test
Suction strainer is pluggedTransmission pump may be noisy if transmission suction screen is clogged. Drain transmission. Remove and clean suction screen. Also, check condition of transmission filter.
Transmission pressure regulating valve is stuck or spring is brokenRemove transmission pressure regulating valve. Inspect for damage
Control valve gasket failureInspect transmission control valve for external leakage. Remove control valve. Inspect or replace gasket.
Transmission pump is failedDo pump flow test

Transmission System Pressure Is Low (One or Two Gears)

Problem

Solution

Failed transmission control valve gasketInspect transmission control valve for external leakage. Remove control valve. Inspect or replace gasket.
Clutch piston or seal ring leakageDisassemble and repair

Transmission Shifts Too Slow

Problem

Solution

Low oil level (aeration of oil)Check and add oil
Low transmission pressureDo Transmission System Pressure Test
Transmission pump suction screen restrictedRemove and clean screen
Low transmission pump flowDo Transmission Pump Flow Test
Excessive transmission element leakageDo Transmission Element Leakage Test Using System Pressure
Oil passages restricted between control valve and transmission elementsemove control valve and inspect oil passages
Clutch cut-off valve stickingRemove and inspect cut-off valve

Transmission Shifts Too Fast

Problem

Solution

System pressure too highDo Transmission System Pressure Test
Stuck modulation valveRemove and inspect modulation valve
Stuck or missing forward/reverse check valveInspect transmission control valve
Broken piston return springDisassemble and inspect clutch

Unit “Creeps” in Neutral

Problem

Solution

Warped disks and plates in transmissionCheck transmission

Transmission Hydraulic System Overheats

Problem

Solution

High oil levelCheck and adjust
Low oil levelCheck and correct
Wrong oil gradeCheck oil grade
Park brake onRelease park brake
Lube lines pinched, restricted, or leakingCheck cooler lines
Unit operated in too high gear rangeOperate unit in correct gear range
Temperature gauge or sender malfunction Installtemperature sensor to verify temperature. Do Tachometer/Temperature Reader Installation Procedure.
Air flow through oil cooler or radiator restrictedDo Radiator Air Flow Test
Oil cooler thermal relief bypass valve stuckBypass thermal bypass valve and check to see if unit still overheats. Do Transmission Oil Cooler Thermal Bypass Valve Test
Oil cooler internally restrictedDo Oil Cooler Restriction Test
Warped disks and plates in transmissionDo Transmission Clutch Drag Check
Leakage in transmission hydraulic systemDo Converter-Out Pressure Test. Do Transmission Element Leakage Test
Low transmission pump outputDo Transmission Pump Flow Test

Excessive Transmission Noise (under load or no load)

Problem

Solution

Engine slow idle too lowCheck engine slow idle speed
Parts worn or damaged in transmissionRemove transmission suction screen. Inspect for metal particles. Repair as necessary
Low or no lubeDo Converter-Out and Lube Pressure Test. Do Transmission Pump Flow Test
Incorrect type of oilChange oil
High oil levelDrain some oil
Low oil levelAdd oil
Air leak on suction side of pumpCheck oil pickup tube on side of transmission

Unit Vibrates

Problem

Solution

Aerated oilCheck and add oil
Failed universal joints on transmission drive shaft or differential drive shaftsCheck universal joints

Unit Lacks Power And Acceleration

Problem

Solution

Engine fast idle speed set too lowCheck fast idle adjustment
Incorrect transmission oilCheck oil
Aerated oilCheck and add oil
Low transmission pressureDo Transmission System Pressure Test.
Warped transmission clutchDo Transmission Clutch Drag Checks
Brake dragDo Brake Drag Check
Clutch cut-off valve stickingRemove and inspect clutch cut-off valve
Low engine powerDo Engine Power Test

Torque Converter Stall RPM Too High

Problem

Solution

Aerated oilPut clear hose on thermal bypass outlet port. Run unit to check for bubbles in oil
Converter relief valve stuck openDo Converter-Out Pressure Test
Torque converter seal leakageDo Converter-Out Pressure Test
Torque converter not transferring power (bent fins, broken stator)Remove and inspect torque converter

Torque Converter Stall RPM Too Low

Problem

Solution

Low engine powerDo Engine Power Test
Mechanical malfunctionRemove and inspect torque converter