I have a 2000 Suburban 2500 4x4 with 180K miles. Last weeekend I was towing my boat which weights about 4000lb and the tranny cooler reading started getting pretty high, up to around 250 when going up some grades. When I got to the flats it went down a little but it stayed around 220 the entire time. My radiator gauge never moved from 190 which it never does. I did replace the tranny fluid about 25K ago so I am sure it is OK. I am just wondering if a Tranny cooler can go bad. I am sure the current cooler is stock and it does not look that big at all. What would be the best thing to look at first? This weekend it was only 82 degrees out and it was running hot so I am a little worried what will happen when the temps hit the 100's. Thanks in advance for any help.