SO, new front differential installed, 4x4 came on when back tires spun in 2x4. Fluid was a little low, added fluid and now it has a vibration in 4x4. Correct amount of fluid, checked it twice, rode it around the yard and rechecked it. Only thing I noticed was where the U joint connects the in input shaft on the diff, its has a slight bit of play up and down. Put a 5/16 fine thread bolt when installed new diff. You think I got a bad diff???????