jlgail4309 wrote:
its a 20 foot box weighs about 3700 loaded. But it eats the fuel pulling. I'm wanting to lower the gear or hold the 4th longer for saving fuel. We tow a lot heading to flordia for Christmas 2nd year its 18 hours 1 way. I think it pulls ok but would help with a 410 gear. Holding 4th should help some.
Wanting to take some mountain trips next year. So a gear or a bigger turbo needs to be in the works.

Sometimes you just have to accept the limitations of your tow vehicle and just drive it in a
sensible manner.
At work, we have a F450 Powerstroke that we use to tow a 24' 16,000 lb trailer. That F450 has
something like 4.11 gears in it. It gets 8 mpg, towing or not towing.
You would think that truck would have no problem pulling that trailer. In fact, the guys had both
the truck and trailer weighed and came in well under the GVW towing limits specified by Ford.
Yet they somehow managed to break the transfer case while towing in 2wd.
Now, you could say that it was just a fluke and the transfer case had a weak part in it.
Or you could say that the drivers shouldn't be lead footin' it and pulling that monstrosity at 80mph.
So even a F450 has some limits as to how much and how fast you can tow even with those drag
racing gears it has.
I agree with the others that its not your trailer weight but wind resistance. Deeper gears will not
help you save fuel and they will not allow you to go at any faster speed.
I dont think a bigger turbo will help much either and besides, your turbo upgrade options are
extemely limited.
Just try to drive it sensibly and within the limitations of a small 4 cylinder diesel.
If you really think your CRD is not up to task, remeber that old chinese proverb:
"There is no substitute for cubic inches."