Locker, spool, posi traction

i had one on my savage, this is what i experienced

pros:
a bit more traction on off road surfaces, works good in sand
power doesnt go to the wheel with less traction
you ALWAYS have 3 wheels with power instead of 2(unless your running rear wheel drive)

cons:
More likely to break a dog bone/cvd
not good for onroad
not good for jumps, cause if you land with just about any amount of throttle you'll snap a dogbone/cvd

I like them, but i would only run one in sand. Im gonna run 100K in my savage diffs, will give it more traction but the diff will still be able to offload if its needs to.

[JOHNNYMAXXIMA]

Definitely don't get it if you are going to be running in the street. I had a spool in both my E-Maxx and T-Maxx and it would always want to slide out during speed runs. It just doesn't track straight under accelleration so I took them out. I was pretty unhappy with it in the dirt as well. Kept wanting to slide out. As far as sand goes, I can't help you out there, I've never driven in it.