I agree with
@Tunedpipe . If you want to upgrade the driveshaft I would go with MIP or Tekno ones. On my slash I have the MIP X-Duty shafts. They hold up on what I'm doing. If you get the MIP ones like I have just make sure that the pins don't fall out because I thought it came with something to cover the pins in the kit but it didn't what I did is put little pieces of tape over the pins.
@Chubaka recommends to put heat shrink over it in this thread:
https://www.rctalk.com/forum/threads/new-mip-driveshafts-for-my-slash.133598/
Also you could try out the
Traxxas Steel ones. Or the Rustler 4x4 ones because I know that the rustler 4x4 ones are more heavy-duty than the slash stock ones.
MIP X-Duty Tekno M6 with hub carriers