Possible causes of poor gear changes in an automatic transmission:
Fluid level and quality:
*Low transmission fluid level
*Old or dirty transmission fluid
Solenoid problems:
* Faulty solenoids that control gear shifting
Problems with transmission mechanisms:
* Worn or damaged gears and gears
* Damaged synchronizers
Electronics problems:
*Faulty Transmission Control Module (TCM)
* Damaged wiring
Slipping or overheating:
* Worn friction discs
* Faulty oil pump
Problems with torque converter:
*Damaged or worn torque converter
* Insufficient torque to change gears
Other possible reasons:
* Worn or damaged gaskets and seals
* Clogged or damaged oil filter
*Damaged gear selector shaft
* Incorrect selector cable adjustment
Diagnostic recommendations:
* Check the level and condition of the transmission fluid.
* Inspect the solenoids and their wiring for faults.
* Read trouble codes using an OBD-II scanner.
*Consult a qualified mechanic for further diagnosis and repair.
Note: It is important to correct the problem as soon as possible to avoid further damage to the transmission.