I am new to off-roading and have a problem that I need help with.  I have an 86 CJ-7 with a DANA 44 in the rear, on my way back from one of my first off-road adventures it started squeaky really bad almost like a high pitched humming noise, so I immediatly pulled over and as i slowed so did the noise and stopped when I did. As soon as I started again the noise increased or decreased as my speed did.  I made it home and started checking things out, I found that the front and rear diff's had milky white oil, so I cleaned them out and replaced the oil. I greased all the zerk fittings on the driveline and any others I could find. I drove around the block and had no noise or any thing for about a mile then it started again. I don't know if it is the driveline or not but after my wife driving it back and forth on the driveway and me crawling on the ground that's where it sounds like its coming from but I'm not 100% sure. Any ideas if I'm right or should I be worried about something else????????????? THANKS FOR ANY HELP.  

GEAR NOISE
Axle gear noise can be caused by insufficient lubricant,
incorrect backlash, tooth contact, or worn/damaged
gears.
Gear noise usually happens at a specific speed
range. The range is 30 to 40 mph, or above 50 mph.
The noise can also occur during a specific type of
driving condition. These conditions are acceleration,
deceleration, coast, or constant load.

When road testing, accelerate the vehicle to the
speed range where the noise is the greatest. Shift
out-of-gear and coast through the peak–noise range.
If the noise stops or changes greatly:
² Check for insufficient lubricant.
² Incorrect ring gear backlash.
² Gear damage.
Differential side and pinion gears can be checked
by turning the vehicle. They usually do not cause
noise during straight–ahead driving when the gears
are unloaded. The side gears are loaded during vehicle
turns. A worn pinion gear mate shaft can also
cause a snapping or a knocking noise.

BEARING NOISE
The axle shaft, differential and pinion gear bearings
can all produce noise when worn or damaged.
Bearing noise can be either a whining, or a growling
sound.
Pinion gear bearings have a constant–pitch noise.
This noise changes only with vehicle speed. Pinion
bearing noise will be higher because it rotates at a
faster rate. Drive the vehicle and load the differential.
If bearing noise occurs, the rear pinion bearing
is the source of the noise. If the bearing noise is
heard during a coast, the front pinion bearing is the
source.
Worn or damaged differential bearings usually produce
a low pitch noise. Differential bearing noise is
similar to pinion bearing noise. The pitch of differential
bearing noise is also constant and varies only
with vehicle speed.
Axle shaft bearings produce noise and vibration
when worn or damaged. The noise generally changes
when the bearings are loaded. Road test the vehicle.
Turn the vehicle sharply to the left and to the right.
This will load the bearings and change the noise
level. Where axle bearing damage is slight, the noise
is usually not noticeable at speeds above 30 mph.  

sounds like a u-joint  

I replaced the u-joints and still I'm having the same issue any suggestions.  

were they bad?  

Check the pinion nut and to be sure its not loose. Push it up and down and pull on it with the drive shaft off. Any movement is bad. Sounds similar to what happened to me. I could feel a vibration in the floor as well. If it increases/decreases with rpm its in the driveline.  

The U-joint looked fine but since I had it out I thought I'de might as well replace. If I remove the driveshaft is there a way to tell if the driveshaft is bad?  Also I will check the pinion nut.  All the help is much apprecited, THANK YOU.  

Look at the drive shaft for any type of dents or dings between the tube welds towards the center. There should be a weight on there. look to see on each end if on may have gotten knocked off.