The output shaft is solid and drives both wheels. There is a "ratchet" mechanism for each wheel that allows each to turn independently (faster forward) of the other. The right wheel mechanism is likely broken/worn out. Look at the parts in the pinion kit (PN 55) for the right wheel. You may find you don't need the actual pinion gear (drive gear) which I'm sure is the most expensive part of the kit. If the other parts of the kit are sold separately, you may be able to fix the mower for less cost. BTW, the only way to KNOW what is wrong with the mower is to disassemble the pinion gear mechanism and examine the parts. If all is well with that mechanism, you look further.

The puck is not visible in the image. The puck is located behind the caliper and in front of the brake disc. You will see the puck after you remove the caliper. Yes, it seems odd indeed. I have mused over this specific situation and I conclude that the unique complaint can only be due to a couple of circumstances. The first one I have already outlined previously in your other thread. The second scenario would be that the entire frame of the tractor is being reshaped during turns because of looseness in frame rivets, or bolts, or screws.......as the case may be. This hypothetical frame reshaping could probably conspire to LENGTHEN the effective brake rod travel when making a left turn (less brake power)......and SHORTEN the effective brake rod travel when making right turns (more brake power). Because there is a "fine line" difference between NO BRAKES and GOOD BRAKES on this mechanical type of disc brake anyhow, just a little difference in the effective length of the brake rod would have a profound overall effect on the stopping power. Study carefully how the frame is put together. Look closely for signs of dry, powdery rust around all the bolts (or whatever is used) that hold the frame together. You might need to wipe around the bolt heads with a clean dry paper towel and then look at the towel to determine if there is any rust (which implies a loose fit condition).

Temporarily unplug the engine connector with the Blue & White wires. The White is the engine kill wire. When grounded, it kills the engine. (Blue is the alternator, so make sure it doesn't short to anything) IF that "cures" the problem, then we know the White wire is getting grounded somehow. Either a bad switch, or worn insulation on the wire itself. Inspect the wire where it touches the chassis etc., to see if there are any bare spots. Note, with this wire disconnected, the engine won't "kill" normally. You might also try unplugging the pedal switch to see what happens. According to the schematic I have, it doesn't have anything to do with cranking the engine, which DOESN'T make sense. The "module" has me stumped, since the schematic doesn't show what it does. Just the plug with Blue Red, Green & White wires. You could also try unplugging it, or wiggling the connector. Sorry I can't add more insight.

Rotor spec for your car is 1.102 nominal, 1.024 minimum thickness. That means when machining my preference is to not go closer than .030 of the discard or 1.054 for the unofficial minimum machining thickness. Rotors of course can be machined off the car and have been for decades. However the preferred method for your car is to machine them on the car. That provides automatic correction for any wheel hub run-out. That's one of the reasons they are fastened to the hub with those two screws. The other reason of course is so that during initial assembly they don't fall off on the assembly line before the calipers are installed. But when you need to remove them, how does a tech do it? I have two methods. One is an impact screwdriver that operates by inertia. There are spiral groves in between the inner and outer portions of the tool, and when you hit it with a hammer and force it to collapse, the inertia of the outer half not wanting to start turning, forces the inner section to try t turn and tighten or loosen a screw depending on the tools setting. Almost every motorcyle tech will be familliar with this tool, they have existed since the 60's at the least. In fact mine is probably the oldest tool in my tool box, having purchased it in the early 70's. But it does not always work, sometimes the screws are simply too tight, and I break the screwdriver bit pretty often. That forces me to use the second method, which ruins the screw. I take a large center punch, and start by making a deep pin hole into the edge of the screw, without hitting the rotor. Once the hole is there, I move the punch to an angle to force the screw to turn by driving it with the punch and hammer. With practice this is really simple and has never failed to remove one of those screws. On a few occasions I have even been able to re-use them. Lastly, 1 1/16" translates to approximately 1.060 (about .030 for 1/32) IMO you would not have been able to machine those rotors successfully, as they would be getting too thin to allow for enough material to deal with the heat generated by braking. Plus six years old on a vented rotor, the rust that builds up in the middle cooling vanes prevents the rotor from cooling efficiently. Plus, the same rusting makes the rotor structurally weaker and prone to "crushing" which is one of the primary causes of rotor thickness variation. All those things together make it unadviseable to have not replaced these rotors when doing the brakes. At the same time we haven't talked about how good the calipers really are, and the caliper slides, how free are they? What about the rear brakes, did you check them? The parking brake assembly? How is the fluid, should it have been flushed? There is so much more to replacing brakes, than just simply slamming a set of pads. That's why you will never see my quote things like the "$99.00 brakes, additional work extra routine".