Ball and trunnion boot replacement

yes, ya know I second guessed you ,I used syn mobil one grease, and I have an extra shaft so I took one off of that ( one side only was missing) Do you think something so minor (they seem awful flat,like a normal washer) could have caused a vibration I had in the car at about 35/40 mph. faster or slower it would go away. I had the drive shaft itself balanced and that didn't help. Well the engine is down so I am going to get the crank and such all balanced.