Got a 2000 ram 4x4 with about 64000 miles on it. I have a squeaking noice that seems to be coming from where the drive shaft goes into the rearend. Does anyone know what this might be? Could my fluid be low, I have not signs of a leak.

 

Probably a dry u-joint, factory ones can't be greased. Look for a rusty stain or powder where the u-joint caps meet the cross. If you see it they're done.
I've also seen a few dry pinion seals. Carefully pull back the lip or the seal and spray some lube in there.
Lithium grease works best IMHO.

 

sounds like u-joint. mine started with a squeak and i ignored it for a few days. then it began to vibrate and when i checked it the seal and all the needle bearings were gone and the cross was flopping around in the cup. to check it get on level ground, in neutral, all pressure off driveline. grab drive shaft and try to wiggle it back and forth against the yoke. should be zero play.

 

from your description : definately U-Joint. Like dhvaughan said : check it for any play. If it's just started making noise, you may not feel it yet. But if it's dry, it will eat the needle bearings up quickly.