there is a mystery whine/whirring noise coming from the rear end that i can't figure out.
the noise is relative to speed.
the noise doesn't change at all in turns.
the noise doesn't change when you baby the throttle or when you get on it.
i'm thinking either pinion bearing or carrier bearings.
with the back wheels off the ground, i grabbed each tire and manhandled it and it didn't budge, so i think the wheel bearings are good.
i changed the transfer case fluid.
i changed the differential fluid. it was a little thin but there wasn't any shavings in there and nothing on the magnet.
the noise started after about 100 miles of driving and now it won't go away.
we changed the u joints in the drive shaft because they were shot.
i grabbed the pinion and wrestled it a little and it didn't budge up/down/side to side.
the temp on the diff cover after a 15 minute drive is about 115º the pinion where it goes into the differential is about 130º, the differential on the front/bottom is about 125º.
also, the end of each axle inside the differential (where the c clips are) are discolored from heat (blueish).
my dad read on a forum that changing the fluid a couple times might make the noise go away.
i don't think the diff is lsd by the way, how would i be able to tell? with both wheels off the ground, when you spin one tire, the other tire goes the opposite direction and when you stomp it you'll get a one wheel peel. so what does the inside of an lSD rear end look like? and what in the world is the exciter ring for?

here's the noise for y'all.

slowing down to a stop
http://www.youtube.com/watch?v=WTXlqa8pX90

taking off easy
http://www.youtube.com/watch?v=wq2GAGBzU4s


i have another video but youtube is having trouble with that one.

 

Have someone hold on to the axle and drive about 5 miles per hour and have them listen to see where its coming from...

And for the record when mine did this (it was more of a squeaking grinding noise) I changed the fluid and its been A Ok ever since. It only took one fluid change though and I think it was making this noise cuz it was low on fluid.

 

the fluid wasn't low, just thin. almost as if water had gotten in there at one point, but not a whole lot because it wasn't too milky.

now you say hold the axle and drive 5mph, that sounds a little dangerous. are you volunteering? do you mean with the back wheels off the ground?

 

in my limited experience in rear ends, once a whine or roar develops, its generally caused by gear or bearing and doesn't go away. it only gets worse. its hardly ever fixed by changing the fluid. sometimes it will quieten down a little with the heavier 140/75 synthetic.

bad pinion bearing and/or ring gear wear will often change pitch between acceleration vs coast. so its sort of a whine at acceleration and a growl at coast.

sometimes you can feel a bad pinion bearing by removing the drive shaft and spinning the yoke by hand.

you might can trace the source of the noise by putting the rear end up on jack stands, and running it in gear. be careful !!! a spinning tire is dangerous.

if you suspect its wheel bearings, those are easily replaced, except that ...
edit - oops, my bad... bearings are tapped into the end of the axle tube, and removed with slide hammer.
not pressed on the axles like i originally said.
see haynes or the service manual download for instructions.

here's a picture of an open diff. the LSD carrier has a lot of crap attached to hold the clutches.
https://dodgeforum.com/forum/2nd-gen...s-or-no-4.html

 

I've never done it before but when this happened to my truck my bud held on to the back axle. I went about 5 mph down my driveway then he yelled stop and said noise is coming from pumpkin... If your dumb about it it can probly be dangerous but he positioned himself where if he fell or something then the truck wasn't going to run him over or anything.

 

the pictures of the lsd didn't work. but the carrier did look simple, just like the d44 but it had bigger spider gears and the exciter ring. and the axle shafts go all the way into the carrier.
do you think the severely worn u joints on the drive shaft could have hosed up the pinion bearing even though the pitch doesn't change between acceleration and coasting?
you should have seen the old u joints, i started to drive them out with a hammer and a socket and it was looking like they were going to be a pain. so i broke out the angle grinder and chopped them off, then popped the caps out with out much resistance. a couple of the caps just had caked on dust in them with no sign of needle bearings.

gav1n8, where was your friends body at when you did the test? was he on a creeper when you did it? i'm just having a little trouble wrapping my brain around how you tested it.

 

oh, i forgot, the funky looking exciter ring drives the ABS/Speed sensor in the top of the diff. the teeth give it a magnetic pulse.

 

thats good to know about the exciter ring.

the truck is about to be on its way back to Tennessee, do you think it'll be ok? you can't feel any vibration or anything while driving, its just that noise. i told my brother in law not to be burning out or romping on it. but the noise does have us a little concerned.

 

That picture in the link was of an open carrier. This is what the trac-lok looks like:

DSCN0499.jpg?t=1262032710

And as far as bearing noise goes, the rear pinion bearing will whine under acceleration and the front bearing will whine under deacceleration. So if its making the same noise all the time, chances are its not the pinion bearings because if the rear bearing is bad, it won't make noise while deaccelerating, and if the front is bad, it won't make noise while accelerating. It all depends on how the differential is loaded.

 

Maybe the driveshaft pushing against the pinon wore something after 100 miles
did the driveshaft go in easily?
lined up?
balanced?
same applies to the universals, did they press together easily? Those needles can fall out and lay at the top of the cup rather than along the side.
It definitly sounds to me like a gear on gear noise IMHO