Had my Redcat Twister XB out today, and after a few minutes heard some 'clicking' from it. You couldn't feel/hear it when you rolled it by hand. I thought that it might have been the pinion/spur mesh, but that checked out fine. So, I started the arduous process of opening up the diff. Opened the case, and.. Nothing. none of the gears were stripped, or even wore down. There wasn't a whole lot of lube in there, so I threw in some heavy grease. Put it all back together, and now there is almost like a 'whirring' coming from it, along with the clicks.

There is also a noticeable binding when rolling the car by hand. No binding when spinning one wheel, but when both turn or one is stopped there is binding and noise from the diff. The drive cups on both the axle and the diff outdrives are a little wore down, but nothing serious. Any ideas? I'm totally lost as to what it could be. Maybe bearings? I've only had it a couple months, and with the snow up here, I've maybe run it less than 10 times.