Automatic Transmission - Overhaul - 4L80-E: Other GMC Pickup C2500

ON-VEHICLE SERVICE

The following components can be serviced without removing transmission from vehicle.

1. Converter-To-Flexplate Bolts
2. Filler Pipe
3. Front Servo
4. Rear Servo
5. Rear Extension Housing
6. Shift Control Cable
7. Solenoids
8. Speedometer Driven Gear & Seal
9. Speed Sensors
10. Transmission Filter
11. Transmission Pan
12. Valve Body
13. Wiring Harness
14. 3-4 Accumulator Assemblies

VALVE BODY

See OIL PUMP & VALVE BODY under TRANSMISSION DISASSEMBLY.

QUICK CHECK

1. Check level and condition of transmission fluid. Check PCM or TCM memory for any stored trouble codes. See GENERAL MOTORS 4L80-E ELECTRONIC CONTROLS article. If no trouble codes are present, go to next step. If codes are present, diagnose and repair all computer-related trouble codes. Clear PCM or TCM trouble code memory.
2. Perform road test. See «ROAD TEST»(ref-25447-S27022574712001042500000) under TESTING. During road test, record shift points. If shift point timing or shifting is incorrect, go to «GENERAL MOTORS HYDRA-MATIC 4L80-E DIAGNOSIS»(ref-55813) article in the AUTOMATIC TRANSMISSIONS section.
3. If shift(s) is too harsh or too soft, see «HYDRAULIC PRESSURE TESTS»(ref-25447-S35843716622001042500000) under TESTING.
4. For specific complaints, see appropriate condition(s) listed under «SYMPTOM DIAGNOSIS»(ref-25447-S12158978212001042500000) .

Oil Out Of Vent Or Foaming

Transmission overfilled. Oil contaminated with antifreeze or engine overheating. Filter not seated. Cross-channel leak causing pressurize in vent area of pump cover.

Transmission Overheats

Low fluid or blocked radiator. TCC stuck in apply or release. Broken TCC valve spring. Cross channel leakage in pump cover. Pressure regulator stuck in high demand. Blocked oil cooler. Problem with converter limit valve assembly. Loss of internal lubrication oil. Problem with stator(s) or turbine seals.

Reduced Internal Lubricant

Cross channel leakage in pump cover. Pressure regulator stuck in high demand. Damaged oil pump mounting gasket. Stuck closed converter limit valve assembly (under heavy load).

High Or Low Line Pressure

Incorrect oil level. Oil pump assembly seals or gears damaged. Pump drive shaft damaged. Pressure regulator valve spring damaged, pressure regulator valve nicked or scored. Pressure relief valve spring damaged. Pump cover leaking (bolts loose). Force motor off or on all the time. Loose connection at PCM or TCM. Possible trouble Code 73.

Loss Of Drive

1. Low oil level. Low oil pressure. Manual linkage misadjusted or disconnected. Damaged torque converter. Leaking or damaged transmission case seals or gaskets. Damaged oil pump drive shaft or pump assembly. Broken bearing, pinion or carrier. Roller clutch damaged or locked.
2. Piston or seal damaged in forward clutch assembly. Forward clutch assembly clutch plates burned, clutch plates missing, or check ball capsule leaking or missing. Burned reaction plate (due to lack of lubrication), broken snap ring or worn gear teeth.
3. Rear gear set assembly pinions, internal ring gear or sun gear damaged. Main shaft damaged. Parking pawl spring broken. Turbine shaft ball not seating.

Forward Motion In "N"

Mispositioned or stuck manual valve. Problem with forward clutch assembly.

Engine Stall

Seized forward clutch, 4th clutch or overrun clutch assembly. TCC stuck on or dragging.

Locked In Park

Damaged parking pawl binding, weak spring or stretched rod.

Vehicle Moves In Park

Manual linkage damaged or disconnected. Broken park pawl spring, park pawl or park pawl gear assembly. Park actuator spring damaged.

Slips In Reverse

Low oil pressure. Reverse servo seal damaged. Reverse reaction drum splines stripped.

No Reverse

Oil pressure low. Reverse servo not correctly assembled, piston or seal damaged, or wrong apply pin. Damaged rear band. Direct clutch assembly clutch plates burned, clutch plates missing, or check ball capsule leaking or missing.

Slips In "D"

Low fluid level. Low line pressure.

No 1st Gear In "D4"

Low roller assembly not attached or race broken. Broken center support race or splines. Damaged case near center support. Center support snap rings not seated.

No 1st Gear In "D2" Or "D3"

Low roller assembly not attached or race broken. Broken center support race or splines. Damaged case near center support. Center support snap rings not seated. Stuck front band.

No 1st Gear In "D1"

Low roller assembly not attached or race broken. Broken center support race or splines. Damaged case near center support. Center support snap rings not seated. Broken housing, or mispositioned or broken rear band anchor pin. Misaligned detent lever.

No 1-2 Shift (1st Gear Only) In "D4"

Output or input speed sensor(s) reads zero. Sun gear splines damaged or missing.

1st & 2nd Gear Only

Solenoid "B" stuck off or not connected to PCM or TCM. Dirt in filter, leaking "O" ring or no supply voltage to "A" solenoid. Stuck 2-3 shift valve. Possible trouble Code 68, 81, 85 or 87.

1st & 4th Gear Only (Manual 2nd & 3rd Only)

Solenoid "A" stuck off. Dirt in filter, PCM or TCM not grounded, leaking "O" ring, no supply voltage to solenoid "A" or wire disconnected. Stuck 1-2 shift valve. Possible trouble Code 68, 82 or 85.

Late 1-2 Shift

Problem with input and/or output speed sensor(s). Faulty digital ratio adapter (2WD only). Wrong PROM calibration. Possible trouble Code 24, 28 or 85.

No Overrun Braking In "D2"

Problem with overrun clutch or reaction sun gear assemblies. Possible trouble Code 28, 68 or 85. Problem with pressure switch to PCM-to-TCM signal.

No Engine Braking

Problem with rear band assembly. Damaged main or output shafts.

No 2nd Gear

Intermediate clutch feed cup plug missing. Problem with intermediate clutch and center support assembly. Damaged intermediate sprag. Broken direct clutch housing or snap ring.

2nd Gear Only

Possible trouble Code 24, 53, 75 and 81.

2nd Gear Starts

Seized intermediate clutch plates. Problem with direct clutch or center support assemblies. Stuck 1-2 shift valve. PCM- or TCM-related problem. Possible trouble Code 82.

No 2nd Gear Braking In "D2"

Problem with direct clutch housing or front band assemblies.

Problem with rear gear set assembly. Damaged main or output shafts.

Problem with overrun clutch or reaction sun gear assemblies.

No 1st Gear In "D3"

Low roller assembly not attached or race broken. Broken center support race or splines. Damaged case near center support. Center support snap rings not seated. Applied front band.

No 2nd Gear In "D3"

Intermediate clutch feed cup plug missing. Problem with intermediate clutch and center support assembly. Damaged intermediate sprag. Broken direct clutch housing or snap ring.

No 3rd Gear In "D3"

Direct clutch feed cup plug missing. Problem with direct clutch and center support assembly. Broken direct clutch housing or snap ring. Solenoid "B" stuck off. Dirt in filter, PCM or TCM not grounded, leaking "O" ring, no supply voltage to solenoid "B" or wire disconnected. Stuck 2-3 shift valve. PCM or TCM problem. Possible trouble Code 81, 85 or 87.

Starts In 3rd Gear

Seized forward clutch or oil holes in driving hub plugged. Damaged or seized direct clutch assembly.

Problem with overrun clutch or reaction sun gear assemblies.

No Engine Braking In "D3"

Damaged main shaft or main shaft bushing.

2nd & 3rd Gear Only

Possible trouble Code 68, 82 or 85. Stuck 1-2 shift valve. Failed solenoid "A" (solenoid "A" off). Dirt in filter, PCM or TCM not grounded, leaking "O" ring, no supply voltage to solenoid "A" or wire disconnected.

No 4th Gear

Problem with 4th clutch or overrun clutch related assemblies. 2-3 shift valve stuck. Failed solenoid "B" (solenoid "B" off). Dirt in filter, PCM or TCM not grounded, leaking "O" ring, no supply voltage to solenoid "B" or wire disconnected. Possible trouble Code 21, 22, 28, 68, 75 or 81.

4th Gear Starts

Solenoid "B" stuck on. Dirt in filter, PCM or TCM signal wire grounded. Possible trouble Code 86.

Note. Digital ratio adapter receives signals from electronic speedometer and sends them to PCM/TCM.

Wrong Shift Points

Problem related to PCM or TCM signal inputs from TPS, speed sensors or pressure switch manifold. Faulty digital ratio adapter (2WD only). Possible trouble Code 21, 22, 24, 28 or 85. Wrong tire size, axle ratio or PROM.

Harsh Shifts

High or low line pressures. Force motor stuck off. Accumulator piston seals damaged or piston springs missing. Accumulator cover bolts improperly tightened or gaskets mispositioned. Missing check balls. Wrong PROM calibration. Possible trouble Code 21, 22, 24, 28, 53, 68, 73, 75, 81 or 85.

Harsh Shifts ("D" To "R")

Blocked direct lube exhaust. Forward clutch spring not working. Direct clutch snap ring broken or not seated. Plugged direct clutch check ball.

Harsh Shifts (3-4 Shift)

Binding 4th clutch spring assembly. Plugged air bleed hole. 4th clutch case bolt blocking oil feed hole.

Harsh Shifts (4-3 Shift)

4th clutch snap ring not seated. 4th clutch spring assembly not working. Plugged 4th clutch housing cup plug. 4th clutch case bolt blocking oil feed hole. Blocked direct lube exhaust port.

Harsh Shifts ("D4"-"D3" Or "D2" Or "D1")

Overrun clutch return spring assembly not working. Plugged overrun clutch housing check ball. Snap ring not seated.

Soft Shifts

Low line pressures. Force motor stuck on. Accumulator piston seals damaged or piston springs missing. Accumulator cover bolts improperly tightened or gaskets mispositioned. PCM or TCM failure. Wrong PROM calibration. Possible trouble Code 73.

Soft Shift (Into "R")

Plugged direct clutch oil feed. Blocked direct lube exhaust port.

Soft Shift (R To "D")

Direct clutch spring not working, large snap ring not seated or plugged check ball.

Soft Shift (2-1)

Intermediate clutch spring assembly not working. Center support snap ring not seated. Center support air bleed blocked.

Soft Shift (2-3)

Plugged direct clutch oil feed. Blocked direct lube exhaust port.

Soft Shift (3-2)

Direct clutch spring not working, small snap ring not seated or plugged check ball.

Soft Shift ("D3" To "D2")

Missing check ball. Incorrect orifice sizes.

No "D2" To "D1" Shift

Broken or disconnected rear band. Incomplete travel of detent lever.

No "D3" To "D2" Shift

Broken or disconnected front band.

No Converter Clutch Apply

Verify proper PCM or TCM operation and vehicle wiring. Damaged wiring harness or pinched wires. Brake switch not working or misadjusted. Solenoid inoperative. Oil pump valve assembly converter clutch shift valve stuck. Converter clutch apply valve stuck. Leaked solenoid "O" ring or blocked screen. Inspect torque converter for external leaks at hub weld area, or unbalanced or contaminated fluid. Turbine shaft seals damaged. Oil pump drive shaft seal damaged. Converter clutch release exhaust orifice cup plug not seated or damaged. Possible trouble Code 21, 22, 28, 37, 39, 53, 75, 81 or 83.

Converter Clutch Does Not Release

PCM- or TCM-controlled TCC solenoid stuck on or does not exhaust. Control valve assembly converter clutch apply valve stuck in apply position. Faulty PCM or TCM. Possible trouble Code 83.

Converter TCC Apply Soft Or Slipping

Leaking turbine shaft seals. Worn oil pump body bushing. Leaking oil hole transfer cup plug. Faulty TCC solenoid. Low fluid.

Converter Clutch Apply Time Wrong

Incorrect output speed sensor, engine speed or throttle position sensor signal. Faulty PCM or TCM. Faulty pressure switch or temperature sensor. Incorrect coolant or transmission temperature (Diesel engine) signal. Possible trouble Code 14, 15, 21, 22, 24, 28, 58, 59 or 68. Problem with digital ratio adapter (2WD only).

CLUTCH & BAND APPLICATION CHART

Gear Selector Position "3" (3rd Gear)

With vehicle stopped, move gear selector to the "3" (3rd gear) position. Steadily increase throttle pressure to accelerate vehicle. Note speeds at which vehicle shifts into 2nd and 3rd gears. see scheme 2or (Scheme 103). Ensure TCC engages while in 3rd gear.

Gear Selector Position "2" (2nd Gear)

With vehicle stopped, move gear selector to the "2" (2nd gear) position. Accelerate vehicle, and note speed at which vehicle shifts from 1st gear to 2nd gear. Accelerate vehicle to 35 MPH. Transaxle should not shift into 3rd gear, and TCC should not engage.

Gear Selector Position "1" (1st Gear)

With vehicle stopped, move gear selector to the "1" (1st gear) position. Accelerate vehicle to 20 MPH. Transaxle should not upshift, and TCC should not engage.

HYDRAULIC PRESSURE TESTS

1. Before performing hydraulic pressure tests, check fluid level and condition. Check manual control linkages for correct adjustment. See appropriate TRANSMISSION SERVICING article. Ensure engine is properly tuned.
2. Connect a tachometer to engine and an oil pressure gauge to line pressure test port. see scheme 3 Compare line pressure to force motor current draw. See «FORCE MOTOR VS. LINE PRESSURE»(ref-25447-S32556210012001042500000).

Note. Hydraulic pressure is controlled by pump output and regulated by computer-controlled force motor. Line pressure is boosted (pressure is doubled) by force motor in the "R" selector position.

Scheme 103

Line Pressure Check

Start engine, and access OVERRIDE FORCE MOTOR on Tech 1 scan tool. Increase force motor current in .1-amp increments. Record line pressure readings and compare to specifications. See FORCE MOTOR VS. LINE PRESSURE table. If pressure recorded is incorrect, see HIGH OR LOW LINE PRESSURE under SYMPTOM DIAGNOSIS.

FORCE MOTOR VS. LINE PRESSURE

SPEED SENSORS/REAR HOUSING

Thoroughly clean transaxle exterior. Drain fluid, and remove torque converter. Place transaxle in holding fixture. Remove rear extension housing. Remove speed sensors.

Rear Band Apply Pin Selection

1. Install Band Apply Selector Pin (J-21370-10) into servo bore. (Scheme 104) Mount Band Apply Pin Selector Gauge (J-38737) and selector pin on transmission. (Scheme 105) Apply 25 ft. lbs. (34 N.m) of torque to hex nut on gauge.
2. Note which step on selector pin lines up with top edge of apply pin gauge; use this information to determine pin length. (Scheme 104)and (Scheme 106). Record length for reassembly. Pins are available in various lengths. (Scheme 106)

Scheme 104

Scheme 105

Scheme 106

END PLAY CHECKS

Using Dial Indicator (J-8001), check front and rear unit end play. (Scheme 107)and (Scheme 108). Front unit end play should be.004-.022" (.10-.56 mm). Rear unit end play should be.005-.025" (.13-.63 mm). Record measurements for reassembly.

Scheme 107

Scheme 108

OIL PUMP & VALVE BODY

Remove oil pump assembly cover bolts. Remove oil pump assembly, gasket and shims. (Scheme 114) Remove valve body assembly. see scheme 46

FORWARD & DIRECT CLUTCH

Using Clutch Remover (J-38358-A), remove forward clutch assembly. (Scheme 112) Using Clutch Remover (J-38733), remove direct clutch assembly. (Scheme 111)

INTERMEDIATE CLUTCH

Remove snap ring. Remove intermediate clutch plates and front band. (Scheme 110)

CENTER SUPPORT & REAR GEAR UNIT

1. Remove center support bolt and discard. see scheme 49 Using Gear Assembly Remover/Installer (J-38868), Adapter (J-21364-A) and Slide Hammer Handle (J-6125-B), remove gear assembly. see scheme 48
2. Remove rear case snap ring. (Scheme 109) Remove rear band and thrust washer. If necessary, select proper selective thrust washer based on end play measurements. See «END PLAY CHECKS»(ref-25447-S31974010972001042500000) under TRANSMISSION DISASSEMBLY. Set thrust washer aside for reassembly.

Scheme 109

Install intermediate clutch plates (4 steel and 4 composition). (Scheme 110) Install backing plate and snap ring. Ensure clearance between clutch plates and backing plate is.040-.107" (1.02-2.72 mm). Using Clutch Plate Aligner (J-24396), align intermediate clutch assembly.

Scheme 110

Apply air pressure into center support hole to hold intermediate clutch plates in place. Using Clutch Installer (J-38733), install direct clutch assembly and front band. (Scheme 110)and (Scheme 111). Using Clutch Installer (J-38358-A), install forward clutch assembly and thrust bearing. (Scheme 112)and (Scheme 115).

Note. Check installed height of speed sensor ring (on forward clutch housing). Top of speed sensor ring to oil pump gasket surface height should be 3.85-3.89" (98-99 mm).

Scheme 111

Scheme 112

OIL PUMP

1. Using Locating Pin (J-25025-1), install oil pump gasket. (Scheme 113) Install selective washer. Using Handle (J-37789), install oil pump assembly. (Scheme 114) Ensure turbine shaft spins free. Tighten oil pump mounting bolts.
2. Using Dial Indicator (J-8001), check front unit end play. (Scheme 107) Front unit end play should be.004-.022" (.10-.56 mm).
3. If front unit end play is not correct, select proper size thrust washer. See «FRONT END PLAY THRUST WASHER»(ref-25447-S08772309952001042500000). If necessary, remove oil pump assembly to change selective thrust washer.

Scheme 113

Scheme 114

FRONT END PLAY THRUST WASHER

Install and secure torque converter. Install rear extension housing. Install speed sensors.

Scheme 115

Scheme 116