Let's say that the lower drawbar is mounted 50 cm behind the rear axle, and 50 cm below the rear axle. The scraper holds 7 ton of dirt of which 2 is on the drawbar. The draft requirement equals the kerb weight of the empty tractor, which is 3,5 ton, of which 2 ton is on the rear axle and 1,5 is on the front axle. The axle heart distance is 2 meter (it's 2,14 meter on my 5245 but 2 meter is easier in this math.)
These are just estimations, close enough to real life scraping to get the general idea.
In the static situation, there is 2 ton at 50 cm behind the rear axle. That's 1ton/meter. At 2 meters from this point (the front axle) this will be 0,5 ton negative front axle load. 1000 kg will remain on the front axle.
This means roughly 4000 kg on the rear axle and 1000 on the front axle.
When the tractor pulls, there are two main points of force: the center of the rear axle, and the center of the drawbar eye. The tractor pulls with a force of 3,5 ton on this tow eye, and the corresponding lever is 50 cm, which causes a momentum of 1,75 ton/meter.
The result 2 meters further up front on the front axle, is 0,875 ton. The front axle load will be the 1000 kg, the outcome of the static calculation (at standstill) plus the dynamic force caused by the pull itself. this is 1000 kg plus 875 kg is 1875 kg on the front axle, and 4000 kg on the rear axle.
The static load index of the 5245 is 1800 kg up front and 3600 kg rear. That is the load to be bouncing on the road at 35km/h. At slow speeds (front loaders) the operators manual mentions a max. dynamic load at speeds below 10 km/h, of 2,5 times the static load rating. The tractor will do just fine, i just dont want to load my front axle that high because the bearing capacity is with front loader use in mind, not with heavy draft applications.
Off course there are loads of variables that have stood out of this calculation, like the reaction force of the wheel torque of the rear axle on the tractor body, which unloads the front axle, reaction forces in the front wheels etcetera. I hope you get the general idea, which is that any drawbar which is mounted higher or lower than the rear axle, causes a reaction force when the tractor starts to pull on this drawbar.