Thanks you all for the great info in this thread. I have read through all 43+ pages and have one simple question: Do you tow in D or 4?
Taking the new boat to the Keys next week. Trip is about 200 miles in South FLorida heat. No major hills other than highway overpasses. Truck is an 08' TRD sport DC longbed. Has the full tow package. TSB was not done but I did add a Hellwig 979 helper spring kit. That has helped a bunch on short trips to the local boat ramp. Boat is listed at 2650 +480 for the motor. Trailer is listed at 850 so I am close to 4k dry. figure another 1000lbs for beer ice, wife and kids stuff i am pushing a bit over 5k. Trailer has surge brakes. Thanks again.
If the truck can hold D without down shifting constantly, just use D. If it keeps down shifting to maintain speeding, then use 4. I tow routinely in 6th with my manual as long as the engine doesn't lug or struggle. If it does, drop it down a gear.