So the other day, while accelerating, I felt an intermittent vibration. Nothing crazy, but I noticed it. Seemed like possibly a u-joint.. I have not heard any actual noise. I had a look underneath today, and the rear diff has some grease covering it, but not terrible. I did notice the vent line was on, but not fully seated on the diff. I cleaned it up a bit, and seated the vent fully. U-joints all seem 100% solid, but they are the originals, with the nylon. I also noticed a bit of grease where the driveshaft goes into the transmission tail housing. To be honest, I remember this had some grease before I had the transmission replaced, back in July, and it didn’t seem very fresh, so I’m wondering if that’s old residue. However, I did notice some play in that area if I pull on the driveshaft. Is this normal..?