rear end squeak?

[shippy]

Brand new to the site and have a squeak I can't quite pin down. I have a stock 2000 Ranger Super cab V6 3.0L 4X4 and recently the rear end was making a loud squeak. Turned out to be the rear U-Joint so I replaced both the U-Joints on the front and rear of the rear drive shaft myself. Job went fairly well and it drove fine for the first 1/2 mile or so and then another quieter squeak developed in the rear drive shaft area. I jacked it up, turned the driveshaft by hand and it's not either U-joint but the new squeak seems to be transmitting through the drive shaft from somewhere in the rear diff.? I can feel it when hand turning it from the rear but not from the front of the drive shaft. No squeak felt in front of the boot where the drive shaft changes diameter from the tranny side but definitely felt it in the rear. There were no ballance issues with the drive shaft and I made sure to score/mark both drive shaft and yoke in front and back and reassembled them as original. The sound is possitively a squeak not a grind or scrape and it doesn't sound like it is the dustcap issue I have read about in other posts. The squeak also doesn't show up until it's been driven about 1/2 mile or so down the road.

Any ideas?