Coils still have mounting points...
And, under lots of torque, you would get pressure on the rear coils to compress them.
As you have opened the diff and found a chipped spider tooth, I would lean towards overall carrier bearing issues. The metal fragments in the oil make for good grinding compound.
Is the play in the carrier, spider gears or pinion?? A lot of play in the carrier indicates the backlash may not be set correct.
I have experienced a cracked bearing race on the pinion that was troublesome to isolate. That provided a clicking sound that varied with speed.
I'll bet that pinion bearing was difficult to diagnose!
as mentioned, I have a little ring/pinion slop, but you would expect some with 175k. Most of my play is in the spider gears, and to my knowledge, the only way to reduce the play is to replace all 4 gears, thrust washers and idler gear shaft. The noise I am hearing dosent sound like a rear suspension noise, I would expect that to make one noise as the play worked out, mine is a continious sorta pulsating creek, as if you had a cracked steel wheel and were driving next to a wall, but there is a lot of pulsations as you take off, that makes me think is is drive shaft speed related and not wheel speed related, I have 3.07 gears.
My first step is to replace the u joints, with 175k on them, it's not a question of if anymore, but when, and they are pretty inexpensive, at the same time I need to replace my pinion seal, it has started to weep and sling oil on the bottom of the Jeep floor.
You have a good point on the RA oil, when I find a set of new spider gears, I will flush out as much old oil as I can and use a magnet on the inside of the housing.
