I myself would not be keen to Stall Test any Tractor in 1st gear with the engine on full bore, 2nd and 3rd speed calm things down some, the danger is knot knowing how good or bad the Brake System is on something you have jumped on for the first time, in a tight Site things can go bad very fast, lots of CAT equipment will drive through the Brakes in 1st speed with all you are doing is damaging the equipment, the Torque Stall Test on a D6D starts off by first doing a speed test on the engine from the low idle setting then the high idle setting, these figures are listed in the CAT Rack Setting chart for the Serial Number of the tractor, then with the engine warmed up as required the Stall test can be done, at High Idle in 2nd or 3rd gear with the brakes firm on the engine speed can be checked to see what speed the engine loads down to, the spec figure is listed to be within it's operational target speed, you would not stall out the Torque for any longer than needed as again all you are doing is harm, I would never Stall Test anything without reason the fact that it's at a Sale Site would put me off more, checking the drive shaft locks when speed/direction is selected at moderate speeds against the brake is about all you need to do unless you have the correct tooling and information to make any judgement on what data you note.
tctractors.