If I had a choice, regarding gearing, I would set up the truck so as not to use overdrive at all when towing. The transmission, whether performance-built or not will stay cooler, and last much longer, if it did no hard work in o/d. The strongest gear in any transmission is the highest gear that is not an overdrive, ie. 3rd gear on these automatics. It's direct drive (1:1 ratio). The whole geartrain is locked together and revolves as one. Torque is not being transmitted between several small spinning members of the planetary gearset, as it is in overdrive.
Just my 2 cents.

 

RE: load range "E" tires.

265/75/16E is rated for 3415# They only started making them a few years ago. Before that 235/85/16E was tops at 3142# for 16" pickup tires.

 

I picked up my new 5th wheel and have found numerous changes needed to be made.

1st - I had to go down and purchase a new Reese 20k hitch (unexpected due to trailer weighed in at 15k empty)

2nd - Loaded with fuel and water and everything else ~17k. I had a problem with the 3.54's pulling the trailer from a dead stop. I had a 0-30 mph in minutes not seconds. It towed great up the hills just so long as I didn't stop. I did not think I would be able to get started again.

Needless to say, I just had 4:10's installed. Mileage sucks and I can't get used to the higher reving when not towing.

3rd - I am not sure how long the tranny is going to hold up. When the truck takes off, I get a really good shutter coming from underneath. I spoke to ATS Diesel and they think that I have a driveline problem not a tranny problem. I then spoke to my driveline shop and he thinks that because the bed sags so much due to the 3800lb pin weight, that my driveline angles are off and causing the vibration. This leads me to looking into purchasing Timbrens. Will these actually help me or do I need to purchase airbags?

Last but not least, I just ordered new RV275 injectors to complement my Edge EZ. I did not want to go overboard with a set of Mach 1.5's until I replace the tranny. That would be a sure way of securing a need for one.

 

If you measured the trailer-only weight while connected to the truck the trailer is even heavier than 17k because some of the trailer weight is carried on the hitch. Even without that factor you are probably a couple of tons over the GCVW so I would expect the truck to strain some.

Still, that is one heavy *****. Which model is it?

 

It is a Nomad Rampage 375 with dual slides and every option including a bunch that are not really offered. We ended up adding a lot of weight that is not on a standard unit.

 

Well, I'm sure that it's comfortable when you finally do get it there..!

 

I pull a 36' Alfa 5er, 11,800 dry, probably somewhere under 14k loaded, 2002 3500, 4.10's, 6 speed. The low gear in the 6 speed gets it rolling easily at idle. The automatic seems like the wrong tranny for that much weight, & taking off could put a severe strain on compnents not engineered for the weight.
I am guessing that you are 2-3k or more over weight, whcih no one seems concerned about, other than things breaking. What happens if you are crusing at 65(or 70), traffic stops suddenly. Can you? Also, say that you are in an accident that you caused & you are found to be overweight, maybe substantially. How will your insurance company feel abou that? How will the Plantiff's lawyer have a field day on that issue. I agree that you can easily tow over the limits, but sometimes the price may be higher than you expect, especially when things go wrong. Even if you do not case an accident, but are involved, it will be used against you. Is it worth it?