Nissan really screwed up the cooling design here... and for this reason alone, I will never own another Nissan as long as I live. The radiator fluid leaks into the transmission fluid, causing the seals to swell. Eventually, my first indication was the inability to back up the truck... like I would literally shift into reverse and apply throttle and nothing would happen. I had to pay $4000 to replace this. The mechanic basically bypassed the internal transmission cooler and went straight to the external cooler in addition to replacing the reverse clutch, valve body, and control module.