ASE · Automatic Transmission/Transaxle (A2) · 8 min read
Transmission Removal and Internal Inspection
- Identify correct procedures for transmission removal, torque converter handling, and engine-to-transmission alignment verification.
- Evaluate internal transmission components, including the case, pump, shafts, gearsets, and differential assemblies, using proper measurement techniques.
- Inspect, test, and adjust holding members, including multiple-disc clutches, bands, servos, and one-way clutches, to prevent hydraulic and mechanical failures.
Transmission Removal and Torque Converter Service
Removing an automatic transmission or transaxle requires careful preparation to prevent component damage and personal injury. On many front-wheel-drive vehicles, supporting the engine with an approved engine support fixture is required before unbolting and removing the transaxle and subframe. On a torque-converter-equipped unit with a converter bolted to the flexplate, follow the manufacturer's removal procedure to disconnect the converter and move it rearward before separating the transmission from the engine. Before moving a removed transmission, secure the torque converter with the manufacturer-specified retainer or another approved method so it cannot slide out and fall.
Engine-to-transmission alignment dowel pins must be present, undamaged, and securely seated in the block or bellhousing. Missing or damaged alignment dowels can misalign the engine and transmission; inspect for misalignment and related pump bushing or converter hub damage before repair. While the transmission is separated, inspect the flexplate for cracks, distortion, and mounting damage; defects can cause noises or vibration, and suspected converter or hub runout should be measured using the manufacturer's procedure. While access is available, inspect the rear main seal and any exposed engine plugs for leakage, then repair confirmed leaks as directed by the manufacturer's service information.
Installing the torque converter requires patience and proper technique. Rotate the converter while pushing inward until its splines and pump drive fully engage. Technicians should verify seating by following the manufacturer's specified measurement or verification procedure rather than relying on an arbitrary count of engagement steps or 'clicks.' Never use bellhousing bolts to pull the transmission against the engine block if the converter is not fully seated, as doing so crushes and damages the front pump housing or pump drive. On a torque-converter-equipped unit, verify converter seating, freedom of movement, and converter-to-flexplate clearance using the manufacturer's applicable checks before attaching the converter. Insufficient converter-to-flexplate clearance before bolt installation indicates an unseated converter, incorrect parts, or another assembly fault that requires immediate correction.
Common mistakes
- Using bellhousing bolts to pull the transmission against the engine block when the torque converter is not fully seated, which crushes the front pump housing or pump drive gears.
- Relying on a specific number of clicks or drops to determine torque converter engagement instead of measuring and verifying seating according to the manufacturer's specified procedure.
- Neglecting to flush and flow-test or replace transmission coolers and lines after a failure, allowing residual metal contaminants to circulate directly into the freshly rebuilt transmission.
- Installing a one-way sprag or roller clutch backward can cause bind-up, freewheeling, shift complaints, or a ratio fault, depending on the transmission design and operating conditions.
Key points
- Follow the vehicle-specific removal procedure: safely support the vehicle and powertrain where required, disconnect the converter from the flexplate on applicable units, and secure a removable converter against falling; if A/C lines must be opened, have the refrigerant recovered with approved equipment before disconnection, never vent it.
- Ensure alignment dowel pins are present and intact; missing or damaged pins can allow bellhousing misalignment and contribute to front pump bushing or converter hub damage.
- Verify converter seating using manufacturer procedures, and ensure the converter spins freely with a specified gap to the flexplate before bolting it in place.
- Check each shaft endplay specified for the unit using the manufacturer's measurement procedure, and correct out-of-spec clearance with the specified selective parts or repair.
- Measure tapered-roller differential bearing preload via rotating torque with an inch-pound torque wrench, using selective shims or threaded adjusters for adjustment.
- Bench-test clutch packs using regulated low-pressure air while wearing eye protection to verify piston movement and detect internal seal or passage leaks.
- After a failure, clean and flow-test or replace transmission coolers and lines as the manufacturer directs; inspect or test a thermal bypass valve if equipped and required, and perform any specified post-repair electronic procedures.
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Sample lesson: Transmission Types and Diagnostic Planning25 practice questions on this exam
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