I am running this with a 13.5 turn motor. The original oil diff that comes with the TB04 PRO2 kit starts leaking badly after just a few minutes of driving. I was very sceptical toward a ball diff. After installing it, i started my run very slowly ( on carpet surface ) but noticed right away the feel to the car. I was very surprised and very pleased to see how well it worked in the TB04 . If you have the same experience that i have, that the original oil diff is starting to leak, do not even think twice. This is well worth the money, and RCMART gives a great service as always.