What are the items for automatic transmission fault detection?
4 Answers
Automatic transmission fault detection items include: 1. Basic inspection; 2. Stall test; 3. Gear position test; 4. Hydraulic pressure test; 5. Road test. The purpose of automatic transmission fault detection is: to determine the technical condition of the transmission through inspection, identify the cause and location of the fault, and take corresponding measures to eliminate the fault. The transmission, also known as the gearbox, is a mechanism used to change the speed and torque from the engine, capable of fixing or changing the transmission ratio between the output shaft and input shaft in different gears. The components of an automatic transmission are: 1. Torque converter; 2. Mechanical transmission; 3. Shift actuator; 4. Hydraulic control system; 5. Electronic control system.
As an experienced mechanic specializing in automatic transmissions for over a decade, these are the most common inspection items I perform: First, check the transmission fluid - if it appears black or has a burnt smell, it needs replacement. Next, use a diagnostic scanner to read trouble codes, with electromagnetic valve codes like P0700 being most frequent. Then test the hydraulic pressure - insufficient pressure indicates issues with the oil pump or filter screen. Also examine the shift solenoid resistance values for abnormalities - last time I helped a neighbor diagnose intermittent resistance in one solenoid causing jerky shifts. Finally, never forget to inspect wiring harness connectors, as flood-damaged vehicles often suffer from corrosion-induced poor contacts. I recommend owners change transmission fluid every 40,000 km to prevent 70% of potential failures.
As a female car owner, I pay more attention to smoothness. When inspecting the transmission, focus on these key areas: whether cold starts delay for more than 2 seconds, if there are clicking sounds during gear shifts when the car is warm; whether the tachometer suddenly surges during rapid acceleration (indicating clutch slippage); if the body shakes strongly when idling in D gear at a red light, it might be a torque converter issue; slow response from the transmission when the reverse camera activates is normal, but persistent stuttering requires checking the TCU control module. I remember last time my car had harsh gear shifts, the technician found metal debris inside the valve body using an endoscope—such internal damage is hard to detect with routine checks.
From an automotive R&D perspective, we conduct destructive testing: 48-hour bench tests simulating full-load gear shifts to monitor clutch plate wear; -30°C cold starts to test hydraulic system response; intentionally contaminating oil with metal powder to observe filtration efficiency. Routine inspections focus on oil temperature sensors (replaced if error exceeds 5°C), turbo speed sensors (signal loss triggers gear lock), and pressure relief valve sealing. Our biggest concern is owners illegally modifying turbo pressure - factory transmissions simply can't handle the extra 50Nm of torque.
