A904 Lock Up 2-3 Shift Issue

The front band only affects 2nd gear so that's not the problem you describe, although it is trashed and needs replaced. Not sure what that cup is. I don't recognize it. The rear band and the front clutch are responsible for reverse. The front clutch is also responsible for 3rd gear. Since you have a problem in reverse and high gear the common factor there is the front clutch. Either the seal is leaking or the clutch plates are toast. You can try an air pressure test to see if the front clutch engages solidly but that won't tell you the condition of the clutch plates. Only way to tell that is to disassemble the trans for an inspection