Should I change all of my transmission fluid?
 

I recently did a drain and refill of my transmission fluid. I hear this replaces about half of the fluid. I was going to do it again to get most of the old fluid out of there. But I have heard from some people at work that have changed all of there transmission fluid, and there tranny went. Their vehicles had high mileage. Mine has 170,000 miles on it.

Wondering if I should do another drain and refill or is replacing half of it good enough?

Nothing bad will happen if you do another drain and refill or two. It's a good idea.
The stories of transmissions failing after a fluid change involve either a power-flush (or worse- a reverse power flush), or a transmission that was already DOA but the friction materials dumped into the fluid kept it running, like the old shyster car dealer's sawdust trick.

thanks I will. If the transmission didn't blow up after the first drain and refill I should be good.