Thanks blu!
I knew there had to be something more than bolt on and go...
Have the rear out and disassembled. Planned on new axles anyway, they will need to be 5/16"longer...
Looks like blue missile got it all figured out and documented.
Quote from blue missile FABO
"OK, here is what I have learned:
Jeep changed their rear disc breaks in the year 1999,They went from an 11.25" rotor set up to a 12" rotor set up on all of the models. Maybe these are the ones everybody's having trouble with.
However before that the 11.25" rotor setup will bolt directly on to the 8 3/4" axle and everything centers up. I even got new pads to check the fit and all is good.
As it happens without knowing this I ended up getting the smaller setup.These were off of a Cherokee not a grand Cherokee.It couldn't fit more perfectly if it were engineered for this axle!Isn't God good!"
(Cherokee not Grand Cherokee brake kit is what I bought!)
There are mods required, detailed in the thread you linked.
Have not received the Kit yet but will update when it gets put together.