Possible reasons for the disappearance of reverse gear on the Passat B5 automatic transmission:
Mechanical problems:
* Wear or damage to the rear planetary friction discs
* Reverse solenoid malfunction
* Breakage of reverse gear teeth
* Timing belt or chain slippage
Hydraulic problems:
*Lack of hydraulic fluid pressure
* Clogged hydraulic filters
* Faulty valve body
Electrical problems:
* Damage to wiring harness
* Faulty shift lever position sensor
* Problems with the transmission control module
How to diagnose the problem:
* Visual inspection: Check the level and condition of the hydraulic fluid.
* Reading Trouble Codes: Use an OBD-II scanner to check for any transmission-related trouble codes.
* Manual Inspection: Remove the transmission pan and inspect the friction discs, gears and other components for wear or damage.
*Checking Hydraulic Fluid Pressure: Use a pressure gauge to check the system pressure.
* Electrical Checks: Check the integrity of the wiring harness and electrical connections.
Ways to fix the problem:
Depending on the cause, the following repair actions may be required:
* Replacement of friction discs, gears or solenoid
* Flushing or replacing hydraulic filters
* Replacement of valve body
* Troubleshoot hydraulic fluid pressure problems
* Repair or replacement of electrical components
It is recommended that you contact a qualified mechanic to diagnose and repair the problem. Repairing an automatic transmission yourself can be difficult and lead to further damage to the transmission.