Truck goes into neutral during hard stop

So whenever I have to break a little extra hard in my Tacoma, the truck seems to go into neutral. If I take my foot off the brake it doesn’t move at all for a few seconds until I either give it some gas and it finally catches, or shift into reverse and then back into drive. Anyone have any ideas? I’m guessing could be a bad torque converter? I’d like to drain and fill the trans fluid but I have no idea the last that it’s been done and I have 180k miles on it so I’m a little nervous about it. I asked my mechanic to do it last time and he said he refuses to do it on older trucks

 

Can't say I have heard this one before. Check the fluid.