First off, I have a bone stock 97 TJ with a 4.0/5 speed with 175,000 miles.
I just noticed when I let out the clutch in 1st aggressivly or accelerate aggressivly from a low speed in 2nd, I hear a creek/clicking in back. A quick visual in back, all looks ok. I did notice play in the input of the rearend, first guess is I need a new set of spider gears. I replaced them about 4 years/50,000 miles ago. Am I the only one going thru spider gears? or is this common?
Back to the problem, I am guessing "U" joints are letting me know it's time to replace them? (they are original)

Your Thoughts?
Doug

If you are going through spider gears, you have another problem.

With the "clicking" sound, perhaps you have a bearing issue.

With a "creaking" sound, I would look at springs and bushings.

The u-joint would be a definitive clunk with vibrations.

The noise only happens when there is a lot of torque to the drive line, thats why I suspected early symptoms of 'u' joints starting to go. Mine is a 97, so it's got coils in back too.

I just took the diff cover off and find a lot of play....again in the spider gears. I also see one tooth that has a small chunk out on the tooth face. Small meaning 1/16 diameter or so, but lots of play.

About 50,000 miles ago I lost teeth on the spider gears causing a failure. I cleaned out the rear and replaced the spider gears and they were much tighter with almost no noticable play in the set, only the ring & pinion slop, which would be normal with 100,000 plus miles.

Still looking for the problem
Doug

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.

Remember, ALL of the bearings are using the same oil...

Replacing the u-joints is a cheap maintenance step with any high mileage setup.

If you are getting leakage out of the pinion seal, consider the downstream connections -- the carrier.

When you flush, you might consider new bearings within the diff, including the pinion bearing. Especially if there is a potential for metal fragments to be floating around in the oil.

Before I did anaything else, I'd find some place to put the rig up on a hoist, put the t-case in Neutral, and have someone spin each rear tire in turn by hand, while you get your ear close to different areas to find out where the noise is coming from. First off, if it's a suspension problem, you shouldn't get any noise with this method. If you do get noise, it would be easy to isolate it to either the driveshaft U-joint, the internals of the differential, or something in the outer hubs. If it's inside the differential, I'd remove the diff cover if you have time and again have someone spin tires by hand while you isolate the bad area.

Good suggestions, and I have done that while I was under checking the differencial. The only tiem I hear the noise is under moderate to hi torque whick I cant do by hand. The only time I did hear it was when I was infront of a shopping center, and was a bit aggressive taking off in 1st gear, I slowed and in second could hear it on briefly on hard acceleration.

I found the problem, a few weeks after i did the above posting, I was out for a short drive and felt a viberation, I dropped the drive shaft and found one of the 'U' joints just starting to fail. I replaced both, the creeking and viberation is gone.