Anyone ever heard of a machine rolling ahead on a lowbed? A Tigercat 880 moved ahead on the lowbed after I hit the brakes doing 20 km. I heard if there is a hydraulic problem, the brakes could be compromised. Johkat
The braking system on most hydraulic motors is only designed to handle a certain amount of load and can easily be overcome with enough force pushing the machine to move, that is why its is very important to secure all loads with enough chains to prevent any movement not just keep it from sliding side to side.
Unless the engine was running, it's a brake problem. And as Ronsii said, you were underweight on chains. I always used to be overweight on chains, got laugfhed at now and then. Seen enough lost or loose and hanging loads to know it takes a lot less time to put a couple extra on than it does to get the machine back where it started and retie.
I can't say for sure on the 880 tigercat , I have experience with the 845s and 822s. The brake system is independent of the track motor except for pressure reduced release line from track motor. The brakes are also more substantial than those I have encountered on excavators. The brakes are spring applied and pressure released. Since the brake pack is out side of the track motor it depends on the planetary gear oil for lubrication . Since the brake are in the middle even having the final oil level slightly low can starve the brake pack. It would imagine it is time to service the brakes.
Come to think of it I must agree with above . How could it move if it was chained properly? Brakes or no.
I always chain everything like it'll free wheel no matter what