After a hard pull on tow vehicle

OP here... Route was from I-5 over to Crescent city, CA state 299. Bunch on construction, with pretty good hills and over 90 degrees. Seamed like I just get going and had to stop for construction one lane several times. Vehicle is 2001 dodge with 5.9 First time I saw temps over 210 in trans. I have BD exhaust brake which works great on freeway speeds. But lower speeds and rpm's not much. Had it in second couple times (on purpose to keep from up shifting and then only to down shift). I've never cleaned out my radiator before. Guess I need to. It's coming up on 90,000 miles. Replaced t-stat couple months ago. My normal coolant temp is about 190. Trailer is around 8,500 pounds. Good info in this posting IMO. I always get egts under 4 before shutting off. Rear end is 4:10 stock (and being 2 wheel drive gets stuck in my own backyard if its wet.)