Hoping I can save some others the struggles i faced. See the picture of the final product. The view is from the front of the rig looking back.
- The two front tanks (one black; one grey) are piped together without room to remove and reinstall new valve or gaskets. (If you do get them in, the gaskets will likely crimp and leak)
- Flush both tanks REALLY well and fully drain them.
- Remove the belly cover and fold out of the way.
- Cut the 3" pipe in the two locations where you see my rubber couplings in the picture.
- Install the driver's side (grey valve) first with the one rubber coupling in place. You'll have enough "play" to get everything in)
- Be sure to put rubber gaskets onto existing flanges first and then slide the valve in place making sure not to dislodge the gaskets.
- Now install the black tank valve with the 3" rubber coupling in place but slid out of the way so you have full freedom to move the pipe mating to the valve.
- Once installed, ensure the 3" rubber couplings are properly straddling the cuts you've made in the pipe.
- Tighten everything up.
- Test for leaks.
- You should be able to complete this in 2-3 hours instead of the 2-3 days it took me.
Good luck!