With a 400# block, I bet if you hooked to something that wont move, your loader would lift the rear tires in the air. And that would be worse than no weight at all, since the entire weight of the tractor + load in the loader would be on the front axle, thats ALOT. With no weight on the 3PH, thats 400# less on the front axle, pluse whatever less it can lift before that tipping point.
The idea is to have enough weight out back to keep it planted on the ground AND take weight off the front.
There have been tons of discussions like this here on TBN.
But basically, think of an arc or rainbow. As you increase the weight out back, you are increasing the load on the front axle UP UNTIL the point in which you can no longer lift the rear tires with the loader. Thats the top of the arc. And then the more weight you add from there on decreases the load on the front axle.
Dont worry about the rear end. People are concerned about 700 or 1000# on the rear of the tractor yet have no issues lifting that much weight with the FEL and putting all that weight over the MUCH small front axles.
Trust me, the rear axle is designed to handle it. A 700# weight is only half of your rated lift capacity back there. Aint gonna hurt a thing.
