Re-geared and free-spinned the 3500 4x4 diesel
 

This week we changed the gearing on the truck from 3.73 to 3.42, installed a Yukon free spin hub kit among other things.
https://www.yukongear.com/spinfree.aspx
The steering box and linkage was replaced, and ball joints as well.
Initial results were very gratifying. In a short test of a few hundred miles, I got about 15% better MPG than the best tank in the previous 15 months of ownership. It was not ideal driving speeds either, some of it over 70 MPH.
I could not be more pumped. The truck is approaching the economy of the 2wd 12V with no aero mods, and retains all the 4x4 capabilities.
If you were to ask how much was due to the spin free hubs and how much was gearing, I'd just grin and tell you I don't care :D

I assume you don't live in a hilly area, correct? Do you have to ease onto the throttle gently when going from idling to drive speed to prevent drivetrain lash, or does it handle that on its own?

It is a normal 2 wheel drive, so there is normal gear lash in the rear differential. The free spin hub kit is for the front axle and keeps all the front drive train from turning unless needed.

Oh! Okay. I thought you installed something similar to a bicycle freewheel. And I thought it was for all wheels. I was questioning the safety of that modification ;)

Oh yeah, that would be bad. I rely on compression braking quite a bit.

The free spin hubs improve coasting greatly. All the driving was on I-5 and other busy roads, I can't wait to do some coasting. I need to put miles on the differential oil so i can change it out, so I will temporarily use the truck instead of the TDI.

3.42 is on my list. Glad it looks good with the free spin.

Steering is the real bear on 4WD CTD. Proper tires will help. Commercial traction such as Bridgestone Duravis line. Wider or with more open space gains little with a mpg penalty.

Better fuel filtration should be top of list. Glacier Diesel and other suppliers. TITAN makes a 56-gl fuel tank (call it 48 useable).

DirecLink brake controller. Modulite for trailer harness.

I am currently running an old set of these on it.
BFGoodrich*All-Terrain T/A KO
So old they are not even listed anywhere. They will wear out soon enough. They were given to me mounted on stock 3rd generation rims, long before I purchased the truck.
I have a set of these, also mounted on stock rims.
Michelin*LTX M/S2
These are not so old and at least 50% tread. I was in the right place at the right time and paid $100 with caps and lug nuts. They go on next.
Note that these are all stock sized 265/70-17. I won't buy other than that size because of towing the 5th wheel. Anything that lifts it up is no bueno.
Lastly, the truck came with 34" Nitto grapplers similar to these on black rims. Sexy but not practical for towing the 5th wheel. I will probably sell these as they are 90% tread and have some value.
Nitto Trail Grappler M/T - LT285/75R17

The steering is all new now, and works great. New box, steering stabilizer, new linkage. New ball joints.
It had a weird "tipping in" to a turn that was cured with the new ball joints. Now it is very similar to my 2wd in feel.
I ordered up a 3 micron filter and base for less than $50, they will go near the tank. The late trucks have a decent electric pump in the tank, but I will also install a fuel pressure gauge at the CP3 pump to make sure it stays happy. This 3 micron pre-filter will be changed often, and the factory ones left on the engine and changed less frequently.
When I get the parts in I will fabricate a mount and hoses, and cut into the fuel line.

All to the good. The LTXs last maybe five years in Texas, so be warned.

KONI FSD developed for ambulances and such recommended. Hendersons Lineup has them and Panhard Rod. Helwig for base rear antiroll (not Big Wig) and upsize front, too.

New aftermarket batt cables recommended. The factory pieces deteriorate internally and RVng/towing is hard on this system. Modulate for dedicated trailer wiring. Separate charge line to house batteries or maybe also TITAN aux frame mount battery.

Michelin tires don't last long up here before dryrotting either.

Are the fresspin hubs just manual locking hubs?