Is there an actual difference in the performance of the Losi Strike if you change the differential lock from the stock one to the ball one?

The ball diff will be an improvement in handling yes. Do you plan on racing your truck?

Am i supposed to say no to that? Thats a yes by the way.

Definitely go with the ball diff. Make sure the diff is lubed if the one you get is assembled without enough diff lube. Adjust it correctly and the slipper should always slip before the diff does on the track. That will make it last. My Strike has the ball diff and a lot of the aluminum stuff to limit the flexibility. I haven't broken much at all and have had a great time with my strike. It looks good too!

How would i knoe if the clutch is going before the diff?

It makes a different sound. You can also take the gear cover off and hold the truck on your table and pull the trigger briefly and see if you can see the spur gear spinning between the slipper plates. If so, then the slipper is slipping before the diff.

thanx for your help