Possible causes of automatic transmission vibration when pressing the brake:
1. Faulty engine or gearbox mounting
* Worn or torn engine or transmission mounts
* Loose mounting bolts
* Deformation of support brackets
2. Problems with the torque converter
* Faulty torque converter overrunning clutch
*Transmission fluid leak
* Clogged transmission oil filter
3. Problems with the brake system
* Unevenly worn brake pads
* Warped brake discs
* Worn brake master cylinder or vacuum booster
* Clogged brake lines
4. Problems with drive shafts
* Faulty CV joints (constant velocity joints)
* Loose drive shaft bolts
* Unbalanced drive shaft
5. Other faults:
* Worn or damaged driveshafts
* Faulty differential
* Faulty speed sensor
Diagnosis and troubleshooting:
1. Visual Inspection: Check for signs of damage or leaks in transmission and brake related systems.
2. Suspension diagnostics: Check the condition of the engine and gearbox mounts, mounting bolts and support brackets.
3. Check the brake system: Check the brake pads, rotors, lines and master cylinder.
4. Reading Trouble Codes: Connect a scan tool to the vehicle’s diagnostic port to scan for trouble codes that may indicate transmission or brake problems.
5. Specialized Diagnostics: If basic visual inspection and trouble code reading are unsuccessful, more specialized diagnostics may be required, such as:
*Checking transmission fluid pressure
* Analyze a transmission fluid sample for metal particles or other signs of failure
* Disassembly and inspection of transmission components
Once the cause of the vibration is determined, appropriate repairs or replacements must be made.