Reasons for failures when shifting automatic transmission speeds:
Mechanical problems:
* Wear of friction discs in clutch packs
* Faulty torque converter
*Low transmission fluid level
* Malfunction of speed or throttle position sensors
* Faulty solenoids or valves
Electrical problems:
*Faulty Transmission Control Module (TCM)
* Damage to wiring
*Weak battery or faulty alternator
Software problems:
* Outdated TCM software
* Incorrect software calibration
Other reasons:
* Worn or dirty transmission fluid filters
* Using the wrong transmission fluid
* Transmission overheating
* Loose transmission mounts
Symptoms of failures when shifting automatic transmission speeds:
* Delay when shifting gears
* Rough gear shifting
* Dips when accelerating
* Sliding gears
* Vibration or noise when shifting gears
Diagnostics and troubleshooting:
1. Check transmission fluid level: Make sure the fluid level is within specification.
2. Perform a trouble code scan: Using an OBD2 scanner, check for transmission related trouble codes.
3. Inspect wiring and connectors: Make sure all wiring is properly connected and undamaged.
4. Check sensors and solenoids: Use a voltmeter or oscilloscope to check that the sensors and solenoids are working properly.
5. Flush and Replace Transmission Fluid: This can help remove contaminants and debris that may be causing slippage in shifting.
6. Replace worn parts: If the friction discs, torque converter or transmission fluid filter are worn, they need to be replaced.
7. Reprogram the TCM: In some cases, reprogramming the TCM can resolve software problems.
8. Contact a qualified mechanic: If you are unable to correct the problem yourself, contact a qualified mechanic for diagnosis and repair.