JFZ90
It helps a great deal. Here is what I have:
The Qantas 380 has the TRENT 972. 36 tons of thrust available at METO. Six tons come out the tail pipe as direct thrust, 30 tonnes are produced by the Fan. The Fan has to pull on something to offset its thrust, this "something" can be a bearing, or it can be a Turbine. The LPT is powering the Fan with effort that obtains to the Fan as 30 Tonnes.
Its reaction to this 30 tonnes it provides impinges on what? To me, the equal and opposite reaction of the LPT is the drag it creates in spinning up to this level of power, less the six tonnes that leave it out the back. I cannot make the Thrust bearing (#1) at the midsection of the LPShaft work, at least not from the diagram. The #2 TB is the most robust, by mm43's welcome cut/pic. You mention axial drag on the Shafts that is not consequential, I am looking for the spot in the powerplant that receives the entire 36 tonnes of thrust, and pushes the a/c through the air. The six tonnes of gas I see as impinging on the #3 TB, that of the HPShaft. Since thirty tonnes of gas (for discussion's sake) have to be accelerated to spin the Fan, I look at the IPT as half the wall of the Cavity as pushing forward on its bearing, it is the beefiest, and surely absorbs the lion's share? That would leave the Fan Shaft. What is it "Pulling" on?? I see it at this point as pulling on the LPT module, which is locked in the engine by the TB #1. Pursuant to barit1's explanation, the tug of war is won by the LPT, always. If this is so, I can envision the LPT itself as providing the anchor for the Fans motive power.
respect,
bear