Automatic Transaxle Overhaul & Testing - 4T80-E: Diagnosis Oldsmobile Aurora II

TROUBLE SHOOTING

Note. Transaxle malfunctions may be caused by poor engine performance, improper adjustments, fluid condition or failure of hydraulic, mechanical or electronic components. Ensure all concerns have been properly checked prior to transaxle overhaul. See appropriate DIAGNOSIS article.

Cleaning & Inspection

Clean transaxle case thoroughly with solvent and air dry. Inspect transaxle case for damage to band lugs, snap ring grooves and drive sprocket bearings. Check for interconnected or damaged oil passages and servo bores. Inspect case for stripped threads in bolt holes or casting porosity. Repair or replace case if necessary.

Disassembly & Inspection

1. Remove snap ring, input sun gear and input sun gear thrust bearing. Remove reaction carrier assembly. Remove reaction sun gear shell assembly.
2. Remove 3rd clutch hub. Remove snap ring and backing plate. Remove clutch plates. Compress spring assembly and remove snap ring and retainer. Remove spring and retainer assembly and piston. Remove seal rings from 3rd clutch housing (if necessary). see scheme 9
3. Check 3rd clutch housing for plugged feed holes. Inspect reaction carrier and sun gear for damaged teeth, scoring or warpage. Check thrust bearing for damage.
4. Check reaction carrier pinion gear end play. Using feeler gauge, measure end play between reaction carrier housing and planetary pinion gear. End play should be.004-.035" (.10-.89 mm). see scheme 10 Check for damage to reaction carrier internal gear. see scheme 9

Inspection

DO NOT wash 4th band in solvent. Inspect 4th band assembly for heat damage, lining cracks and separation. Check band stop for damage and replace if necessary.

Remove snap ring and disassemble clutch plates. Compress spring assembly, and remove snap ring and retainer seat. Remove spring and retainer assembly and piston. see scheme 12 If necessary, remove 2nd sprag. Spiral snap ring must be replaced if removed from 2nd sprag. Check clutch housing for plugged feed holes. Inspect clutches for wear and piston for cracks or damaged check ball. Inspect 2nd sprag for damage.

1. Position clutch plates on bench. Compress spring assembly, and remove snap ring. Remove spring assembly and piston from driven sprocket support. see scheme 14 Remove 3rd clutch exhaust valve from driven sprocket support.
2. Check driven sprocket support for plugged feed holes or damage. Inspect clutches for wear and piston for cracks or damaged check ball. Inspect 3rd clutch exhaust valve for scoring.

Remove snap ring, parking lock gear and thrust bearing. Remove forward clutch support assembly with low-roller clutch. see scheme 17 Separate clutch housing from coast clutch hub and thrust washers. Remove final drive sun gear shaft. see scheme 15- see scheme 17. Using feeler gauge, measure input carrier housing-to-pinion gear end play. End play should be.003-.035" (.08-.89 mm). see scheme 18

Disassemble clutch support. Remove and discard oil seal rings and oil cooler return seal. see scheme 17 Inspect all parts for damage or wear. Replace bushing if worn.

1. Remove snap ring from forward/coast clutch housing. Remove backing plate, forward clutch, Belleville, coast clutch and apply plates from housing. Compress spring assembly and remove snap ring.
2. Remove coast clutch piston, apply ring, forward clutch piston and seals. see scheme 15 Inspect clutches for wear and piston for cracks or damaged check ball.

Scheme 1

1. Place NEW seals on forward clutch piston, and install in housing. Install forward clutch apply ring. Place NEW seals on coast clutch piston, and install in housing. Install spring assembly. Using appropriate compressor, apply pressure to spring assembly and install snap ring. Install backing plate, forward clutch, Belleville, coast clutch and apply plates in reverse order. see scheme 15 Install clutch assembly snap ring.
2. Install thrust bearing to back side of forward/coast clutch housing. Connect forward clutch support to forward/coast clutch housing. Assemble coast clutch hub with thrust bearing, input internal gear and flange into forward/coast clutch housing. see scheme 16 NOTE: When splines of coast clutch hub and forward sprag outer race are properly engaged, input carrier will drop below forward/coast clutch support hub. Ensure a dull metal sound is heard during engagement. Distance from top edge of forward/coast clutch housing to top edge of input internal gear should be about.886" (22.50 mm). (Scheme 1)
3. Install input carrier and reaction internal gear with thrust washer onto input internal gear. Install final drive sun gear shaft. Install thrust bearing and parking lock gear. Install snap ring. see scheme 16and see scheme 17.

1. Inspect final drive internal gear for damaged teeth, worn bearing surfaces, or damage to differential and pinion gears. Inspect sun gear, thrust bearings and speed sensor ring gear for wear or damage.
2. Check final drive carrier pinion gears for excessive end play. Measure end play between carrier and pinion gear thrust washer. End play should be.008-.012" (.20-.30 mm). see scheme 18 Replace final drive carrier if clearance is not within specification.
3. Using pin punch, drive differential pinion shaft retaining pin from carrier. Remove pinion shaft, pinion gears and thrust washers. see scheme 23 Remove side gears and thrust washers.
4. Remove sun gear-to-carrier thrust bearing. Using screwdriver, pry final drive sun gear from final drive carrier. Inspect all parts for damage or abnormal wear. Inspect final drive sun gear shaft for damaged splines or journals.

Inspect output shaft snap ring groove, splines, journal and shaft surface for damage. Replace if necessary.

Disassembly, Inspection & Reassembly

1. Remove accumulator housing from channel plate. Remove 4 check balls. Remove accumulator spring from channel plate. Remove transaxle pressure switch assembly from lower control valve assembly. see scheme 25
2. Remove "E" clips from accumulator shafts on top side of accumulator housing. (Scheme 2) Remove 1-2 and 3-4 accumulator assemblies (piston, "O" ring, spring and shaft).
3. Remove cover from accumulator housing. Remove forward and reverse accumulator assemblies. Check all parts for wear or damage and replace as necessary. Lubricate all NEW seals with ATF. To reassemble, reverse disassembly procedure.

Scheme 2

Clean valves, springs and bushings in solvent. NEVER use shop rags to clean valve body components. Inspect valves and bushings for scoring, nicks and scratches. Inspect springs for damaged or distorted coils. Inspect valve body casting for porosity, interconnected oil passages and damaged machined surfaces.

Inspect pump body for porosity, interconnected oil passages, or damaged inner pump area surface or machine facing. Check oil pump gears for damage. Check oil pump shaft and thrust washer for wear or damage.