Trying to diagnose a low but consistent "warbling" noise coming from my jeep. Trying to resurrect my baby and have done a lot under the hood already... too much to list out here right now. Currently she purrrrs like a kitten but something in the axles/wheels/drivetrain is "warbling" pretty much all the time over 10mph(can't really hear it once you get up to 50+mph) during acceleration AND while coasting. No noise at idle. A few things to lay out first:

1.) I have a short arm 3 inch lift with 1' inch transfer case spacers, 31's, and some FLAT leaf springs in the rear. 1st owner did add a leaf and know these need to be replaced regardless.
2.) front driver's side outer axle seal is leaking oil badly. You can see that the knuckle is covered in wet grime.
3.) 197K miles on stock Dana 30 in front, and Chrysler 8.25 in rear.

This noise is consistent but not overpowering while accelerating and coasting. Sound like "warbly" maybe dry "grindy" gears if I had to guess? So, first thought was to check the wheel bearings on each corner. Jacked her up and checked for play in each wheel individually. Rear driver's side wheel is the only one with approximately 1/16- 1/18 inch in play with a bit of a "clank". Other 3 are rock solid. It's a Chrysler 8.25 also in pretty bad need of a diff oil drain and new gasket. Looks leaky. Maybe the rear wheel bearing or more likely something inside the axle? a seal or the internal gears and/or seals need to be rebuilt? Anyways, I'll be pulling the cover to take a look regardless.

Main question overall is where to check next for diagnosis of noise? Drive shaft u-joints, wheel u-joints, or just dig into that rear axle? Thanks for any veteran advice ahead of time.

 

See below.

 

Let the hunt for the noise begin...

I'll preface by saying I totally understand when people ask this type of question that it is exceedingly difficult to diagnose without more information/data. That said, I intend to solve this issue one way or another and will follow-up with results on this page. I truly appreciate all the advice given to me in prior instances by some very wise jeepers on this forum and never get mad when my posts don't get a response. Honestly, thank you.

What I started with so far:

• Changed engine oil (have had a recent Blackstone labs reading within the year in this thread: https://www.cherokeeforum.com/f2/200...report-249837/,"Averages show typical results for these 4.0L engines after ~4,000 miles of oil use")
• Changed transmission fluid (Dex/Merc III) *I did not remove the pan nor did I replace the gasket or filter underneath, just a drained and re-filled. **Old fluid came out clean/red looking, and measured it out to approximately 3 quarts
• Changed the transfer case fluid (Dex/Merc III) *Old fluid came out clean/red looking
• Rear Diff (Chrysler 8.25): removed cover, cleaned mating surfaces, inspected the teeth of the gears, cleaned inside of gears out with a bit if brake cleaner, applied lube locker gasket and re-installed with fresh 75w90 gear oil
• Front Diff(Dana 30): pulled drain plug and it was showing wet oil (my thought was that it may be dry in there due to my axle seals leaking badly and the steering knuckle being covered in grease) and topped it off with fresh 80w90. Took about 1/2 of a new quart, so it is definitely leaking but not bone dry. Sidenote: I do intend to replace the inner axles seals this weekend and inspect the front diff gears/carrier and axle shaft up close.

So all the drivetrain fluids are full and nothing is dry or appeared to be dry beforehand, so I got that going for me which is good. Drove it around and the noise is still there. It's really noticeable(but not overwhelming) in a flat smoothly paved parking lot or while coasting around 20mph.

Next Steps I have planned:

• Remove REAR drive shaft and drive around in 4H to see if noise goes away. If so, I'll replace both u-joints
• Remove FRONT drive shaft and drive around in 2H to see if noise goes away. If so, I'll replace both u-joint
  • *I did get underneath the jeep while it was in neutral and pulled up and down and sideways back and forth around all 4 yokes/u-joints. There is the slightest of play(maybe 1/16th or 1/32nd of an inch) in a 2 or 3(can't remember), but pretty darn minimal.

If none of that works:

• Double/Triple check front wheel bearings and replace if needed
• Wheel u-joints?
• Pinion bearings in front and rear differentials?
• Something else within the driveshafts like the race around the yoke or the yoke itself?

Gonna keep hunting down this ghost and will report back...

 

I’m interested to see what you find. I have a weird soft/quite grinding sound that I can’t seem to pinpoint. It sort of sounds like when you spin a brake drum with the shoes just touching it. Same deal here, it starts around 10 mph and doesn’t get any louder or quieter at different speeds. I can hear it pretty well in the driver seat, I had a buddy drive it and I could barely hear it while riding in the passenger seat. My buddy told me to just turn the radio up a bit and stop worrying about it

 

took front driveshaft off today and drove it around in 2H (u-joints looked in decent shape and slip joint on shaft was plenty greased with no play).... still growling out of the front end it sounds like somewhere. will remove rear driveshaft tomorrow and drive around in 4H, just to narrow it down. Thinking it's more likely front end wheel bearing/hub assembly or pinion bearings in dana 30. Maybe just driveshaft grinding on sh*tty inner axle seals.