jetboater

one option since they're new tires is to switch them side to side and see if that helps

Since you ran the spare on the rear, I'd change out the diff fluid no matter whether the pulling is coming from the tires or not.

changing the diff fluid is not an expensive repair---you can do the diff fluid change in about 30 minutes for less than $30--and that's assuming you have to spend $20 for the tools

Check the fluid for metal shavings---if they're not any larger than very small flecks of metal and you're hearing no unusual noise from the diff, hopefully it should be fine.

warrenk05

check if there is any uneven wear in the front and the backs. mines kept drifting to the right due to uneven backs.

omg_miiiike

Dude I've seen 3 threads on this in the past week.. Mine is doing the same thing.

I purchase my tires used because I go through them often because of my camber, I am thinking it may be the thread on mine also now.