I have a TC4 and I ran the spool in the front a couple times it works good if your on a high speed track with good traction. you can come in hard and the push is ok and when you go out of the turn just pull the trigger and go for it. With the spool you have to commit completly to the exit. so if your on a small track and you have to ease out of the turn you will be breaking traction and the car will tend to as I call it, "tic toc" the front will slide as you come in and then the back will slide as your in the turn and then when you punch it the back will fall out again. So you have to slide into the corner and then make the front drag the rear end out by just yanking on the power..that is what has worked for me. but in all honesty I pulled the spool out and just run the front diff a little tighter than the rear and that seems to work good all around. For some real fun put the spool in the rear and do some drift racing LOL