Final answer:
If a vehicle is not stable on jack stands, lower the vehicle, reposition the jack stands, raise the vehicle again, and check for stability before working underneath.
Step-by-step explanation:
If the vehicle does not appear to be stable on the jack stands, it is critical to ensure safety before proceeding. You should not work under a vehicle that is not securely supported. If instability is detected, you should immediately cease any work. The correct course of action is to:
Lower the vehicle carefully back down off the jack stands.
Reposition the jack stands to ensure that they are placed correctly under the vehicle's designated lift points and the ground is level and solid.
Carefully raise the vehicle again and place it onto the repositioned jack stands, ensuring that the vehicle is stable before any work is performed underneath it.
It is never safe to work under a vehicle that is not properly and securely supported by jack stands. Always take the time to double-check the placement and stability before getting underneath a vehicle.