Originally Posted by
6CylBill
In no way do I want to disrespect you. What I'm about to say is simply an opinion and thoughts. My thoughts are few and far between and my opinion is formed by information learned from reading, not so much real world experience.
It's my personal opinion when towing anything heavy you should keep the truck out of OD, especially with a highway gear ratio. The truck and engine might be able to pull 2,000 lbs with no issue, but it's harder on the transmission due to it kicking in and out of OD more.
Just because your truck can pull it with a highway gear does not mean that you should. Pulling a load heavier than what the truck is rated to tow with said gearing can really load down the engine and transmission and all the parts inbetween. If you have the means to do so a gear swap isn't a bad idea if you plan on towing heavy loads regularly. I know of men who pull loads all the time with highway gears and they have no problems. All I'm saying is use common sense for your truck's sake and for your own wallet's sake. Instal coolers and keep an eye on th tempature and fluids.
Make sure your truck can STOP! Very important. ha ha!
All that I'm saying is that it's better for the truck, engine and transmission if you are geared for the load and know when to turn the OD off. Don't just jump in the truck and GO and never think about the load on the engine or tranny.
This isn't directed to the OP or anyone. I'm not trying to insinuate anyone here does this. I think all the posters here who pull heavy loads regularly know how to drive. 
Just trying to be helpful!
Bill
Check his sig; he's got an M5OD and 4th ain't overdrive. 2000RPM in his truck is around 50mph in 4th. M5OD trucks even have a warning on the sun visor saying stay out of 5th when towing.
Last time I did major interstate hauling I wished I had an automatic because of the smooth, seamless shifting.
I will give 6.2D some credit- the high stall converters on newer automatics loose the ability to use low-RPM torque and "finesse" a load. The converter on my old Mercedes was stiff as wet cement, and I could lug smoothly through the snow where most vehicles were just spinning tires. I think it's mainly for MPG/emissions purposes so the engine isn't "under load" sitting at a stoplight. Other times, manufacturers are using high-stall converters to compensate for super-high "economy" rear ends. My wife's Impala is a pain to drive in traffic with the 2.86 axle and factory 2000RPM converter (final drive on the highway is 2.0:1!). In the old days, you had to stand on the brake to keep the car from creeping forward at 5mph. Now you have to burp a modern automatic to 1200RPM (or higher) just to move an inch!.