I had a clunking noise coming from the rear end found out I had the driver side rear axle rear chipped a couple of teeth. I replaced it put the rear end back together double checking everything even putting parts back on the same side to make sure if one side was wearing different they would match back up in hopes that I would be done with it. Took it for a test drive and it seemed perfect.... until I reached 25 mph or above and I'm getting a weird sound like a rhythmic rubbing sound, speed up it speeds up slow down it slows down. Get back under 25 mph and it disappears completely. It has the Eaton G80 locking differential and drums on the back. Any Ideas of where to start looking would be appreciated.

 

Did you change all 4? If not, change all them, if so, it might be ok to run it till they get a wear pattern.

 

I only changed the 1 seeing the $200 price tag and since money is tight. Just took to the store and the noise has changed now it's sounds like a chain dragging and bouncing behind me like a ting ting ting sound.

 

What had a couple of chips?? spider gears,ring or pinon gears..?.You cannot in most cases_._no strike that in any case just put a rear back together without checking preload.
This takes a dial indicator ,marker grease i use a yellow tire crayon and a crush sleeve,or shims,or how ever the manufacturer uses to set proper pinon-gear preload to the ring gear.
If that is the case_STOP_driving the truck and let someone do that or you will trash your rear diff.