Possible causes of strong shocks when changing gears in an automatic transmission:
Mechanical problems:
* Worn or damaged friction discs or bands
* Clogged or faulty valve body
* Faulty torque converter
* Faulty gear shift mechanism
Hydraulic problems:
*Low or contaminated transmission fluid
* Faulty oil pump or filter
*Leaks in the hydraulic system
* Clogged shift solenoids
Electrical problems:
* Faulty output shaft speed sensor
* Faulty transmission fluid pressure sensor
*Faulty transmission control module
Other possible reasons:
* Worn or damaged engine or transmission mounts
* Incorrect driveshaft mounting
* Incorrect shift cable adjustment
Troubleshooting steps:
1. Check the level and condition of the transmission fluid.
2. Scan trouble codes using an OBD-II scanner.
3. Visually inspect the transmission for leaks or damage.
4. Diagnose the hydraulic system by checking transmission fluid pressure and flow.
5. Check electrical connectors and wires for damage or looseness.
6. Contact a qualified mechanic for further diagnosis and repair.
Notes:
* Driving with strong shocks when shifting gears may cause further damage to the transmission.
* It is important to identify and eliminate the cause of the problem as soon as possible to avoid costly repairs.
*If you are unsure how to fix the problem yourself, seek professional help.