ASE · Automatic Transmission/Transaxle (A2) · 7 min read
Transmission Assembly and Installation
- Perform critical internal assembly checks, including clutch pack clearances, regulated air pressure testing, end play adjustment, and valve body servicing.
- Execute pre-installation inspections of the engine block, flexplate, alignment dowels, and torque converter seating to prevent catastrophic mechanical failure.
- Complete post-installation procedures, including fluid cooler servicing, linkage adjustment, transmission fluid level verification, control module relearns, and road testing.
Internal Assembly, Clearances, and Valve Body Service
Rebuilding an automatic transmission requires precise verification of internal clearances before the unit is sealed. Transmission assembly end play must be measured and adjusted using selective thrust washers or shims according to manufacturer specifications. Similarly, clutch pack clearance must be verified before final assembly. Technicians measure clutch pack clearance using the method specified in the manufacturer's service information, such as a feeler gauge or dial indicator, and compare the reading to the approved range. When the manufacturer's procedure calls for an air check, apply regulated air to the specified passages at the specified pressure and stage of assembly; wear eye protection and keep hands clear of components that may move.
The valve body controls hydraulic routing and requires meticulous care during assembly. Check balls must be installed in the exact locations and quantities specified in the manufacturer service information; a misplaced or missing check ball alters hydraulic circuit timing and pressure. Technicians must inspect valve body separator plate gaskets and screens for contamination or damage, replacing them whenever damaged or required by the manufacturer's service procedure. In addition, manual and hydraulic spool valves must be inspected for free movement in clean, properly lubricated bores using the manufacturer's procedure, keeping in mind that return springs or other components may prevent a valve from sliding under its own weight.
Improper mechanical fastening of the valve body is a frequent cause of comebacks. Uneven tightening or overtorquing of valve body fasteners can distort the valve body casting and cause hydraulic valves to stick in their bores. To avoid distortion, valve body bolts must be torqued in the manufacturer-specified sequence and to the specified torque value. Finally, route internal transmission wiring harnesses away from moving mechanical parts, secure them in factory retaining clips, and inspect internal solenoid connectors for damaged terminals, broken locking tabs, or corrosion before installing the pan.
Common mistakes
- Using bellhousing bolts to pull the transmission against the engine block when the bellhousing does not sit flush by hand, cracking the fluid pump gears and damaging the pump pocket.
- Failing to verify torque converter seating depth before installation can leave the converter's pump-drive features unengaged and damage the pump when the bellhousing is tightened.
- Neglecting to inspect or reinstall required engine-to-transmission alignment dowels can cause misalignment and may lead to front pump bushing damage or flexplate cracking.
- Arbitrarily clearing transmission adaptive values or failing to input solenoid flow data when replacement procedures require specific scan tool calibration and relearn steps.
Key points
- Verify clutch pack clearances and end play by the manufacturer's methods, adjust them with the specified selective parts where applicable, and air-check clutch circuits at the stage directed by service information.
- Torque valve body bolts in the specified sequence and to the proper torque value to prevent casting distortion and sticking spool valves; ensure check balls match factory quantity and placement.
- Inspect alignment dowel pins, flexplate condition, and the crankshaft pilot bore; missing dowels can cause misalignment and contribute to flexplate cracks or front pump bushing failure.
- Verify torque converter seating depth by measuring from the bellhousing face before assembly; the bellhousing must sit flush against the engine by hand without pulling it in with bolts.
- Flush or replace fluid coolers and lines after internal failures, replacing non-flushable micro-channel coolers and testing thermal bypass valves as required.
- Adjust the shift linkage so detents match the indicator, and verify that the transmission case vent is unobstructed to prevent elevated internal pressure and leaks.
- Fill fluid using the exact manufacturer procedure and formulation, perform required electronic calibrations and relearns, and verify operation and leak-free performance during a road test.
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Sample lesson: Transmission Types and Diagnostic Planning25 practice questions on this exam
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