When pulling against the trailer after pushing in the tractor valve, what should happen?

When the tractor valve is pushed in, it indicates that the trailer's emergency brake is released, allowing the air brakes of the trailer to engage properly. During the process of pulling against the trailer, it is expected that the truck should not move. This is due to the fact that the trailer's brakes are disengaged, and the coupling between the tractor and trailer should be secure.

If the truck does not move, it indicates that the connection is solid, and the tractor is properly engaged with the trailer. This condition is essential for safety, as it confirms that the braking system is functioning correctly and that the truck is ready for transit without any slippage or unwanted movement.

Other situations like the truck moving forward or the trailer shifting would indicate potential issues with the coupling or braking systems that would need to be addressed before proceeding.