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Troubleshooting - Construction & mining parts for Volvo, Allison, Funk & ZF. | Centranz, Inc.

Transmission Slippage

Problem

Solution

Low oil level Check and add oil
Wrong oil grade Check oil grade
Weak or broken pressure regulating valve spring Do Transmission System Pressure Test
Transmission pump suction screen restricted Remove and clean screen
Low transmission pump flow due to worn pump Do Transmission Pump Flow Test
Transmission control valve or gasket leakage Remove valve and inspect gaskets
Clutch cut-off valve sticking Remove and inspect clutch cut-off valve
Restricted modulation orifice housing orifices Remove control valve housing and check for restrictions in valve and valve
Excessive transmission element leakage Do Transmission Element Leakage Test Using System Pressure
Worn clutch disks Repair transmission

Unit Will Not Move

Problem

Solution

Low or no transmission pressure See Transmission Pressure is low (all gears) or Transmission Pressure is low (one or two gears)
Service brakes will not release Do Brake Pedal Operational Check. Do Service and Park Brake System Drag Checks
Park brake applied or parkswitch misadjusted Adjust park brake switch
Stuck control valve spool Check shift linkage operation. Disconnect shift linkage from control valve spool and check linkage movement.
Failed torque converter Do Torque Converter Stall Test. If engine pulldown is normal, torque converter is good
Broken shafts or gears Drain transmission to determine if large pieces of metal contamination are present
Broken drive shafts Inspect drive shafts and universal joints for external damage. Repair
Broken ring or pinion gear If 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 level Check transmission oil level and refill if necessary
Switch failure Verify transmission system pressure. Do Transmission System Pressure Test
Suction strainer is plugged Transmission 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 broken Remove transmission pressure regulating valve. Inspect for damage
Control valve gasket failure Inspect transmission control valve for external leakage. Remove control valve. Inspect or replace gasket.
Transmission pump is failed Do pump flow test

Transmission System Pressure Is Low (One or Two Gears)

Problem

Solution

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

Transmission Shifts Too Slow

Problem

Solution

Low oil level (aeration of oil) Check and add oil
Low transmission pressure Do Transmission System Pressure Test
Transmission pump suction screen restricted Remove and clean screen
Low transmission pump flow Do Transmission Pump Flow Test
Excessive transmission element leakage Do Transmission Element Leakage Test Using System Pressure
Oil passages restricted between control valve and transmission elements emove control valve and inspect oil passages
Clutch cut-off valve sticking Remove and inspect cut-off valve

Transmission Shifts Too Fast

Problem

Solution

System pressure too high Do Transmission System Pressure Test
Stuck modulation valve Remove and inspect modulation valve
Stuck or missing forward/reverse check valve Inspect transmission control valve
Broken piston return spring Disassemble and inspect clutch

Unit “Creeps” in Neutral

Problem

Solution

Warped disks and plates in transmission Check transmission

Transmission Hydraulic System Overheats

Problem

Solution

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

Excessive Transmission Noise (under load or no load)

Problem

Solution

Engine slow idle too low Check engine slow idle speed
Parts worn or damaged in transmission Remove transmission suction screen. Inspect for metal particles. Repair as necessary
Low or no lube Do Converter-Out and Lube Pressure Test. Do Transmission Pump Flow Test
Incorrect type of oil Change oil
High oil level Drain some oil
Low oil level Add oil
Air leak on suction side of pump Check oil pickup tube on side of transmission

Unit Vibrates

Problem

Solution

Aerated oil Check and add oil
Failed universal joints on transmission drive shaft or differential drive shafts Check universal joints

Unit Lacks Power And Acceleration

Problem

Solution

Engine fast idle speed set too low Check fast idle adjustment
Incorrect transmission oil Check oil
Aerated oil Check and add oil
Low transmission pressure Do Transmission System Pressure Test.
Warped transmission clutch Do Transmission Clutch Drag Checks
Brake drag Do Brake Drag Check
Clutch cut-off valve sticking Remove and inspect clutch cut-off valve
Low engine power Do Engine Power Test

Torque Converter Stall RPM Too High

Problem

Solution

Aerated oil Put clear hose on thermal bypass outlet port. Run unit to check for bubbles in oil
Converter relief valve stuck open Do Converter-Out Pressure Test
Torque converter seal leakage Do 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 power Do Engine Power Test
Mechanical malfunction Remove and inspect torque converter