A few questions:

What weight oil is in the diff stock (or is it the black grease)? I got one off ebay from a B4.1 RTR.

I believe you guys about the diff oil wieght, but looking back into threads, I thought many sc10 drivers thought 1k was too thick. They were going with 20w shock oil or black grease. 10K for outdoor and 3k for indoor seems thick in comparison.

How full are you filling yours. In 8th scale, I used to fill to the cross pins, to leave room for expansion due to heat. I know you can overfill them.