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?

yes. I was glad I did them when I did. I had one axle u-joint bad and one that was going. Now I am new across the entire front axle, new bearings seals u-joints. Friday I get to do some 2wd low maneuvering on our first camp outing.

How much does a new front and rear ring and pinion gear swap cost? Did you do the swap or take it to a shop? Both of my dodge trucks have 355 gearing that is apropriate for my travel trailer towing. If I went with a taller gear, it might take me out of the optimum efficiency range on the highway. Free spin sounds nice avoiding a lot of driveline friction. In my opinion, you have the best generation dodge. The p7100 injection pump is superior to he vp44 in my gen dodge. I ppumped my 99, but not my 98 yet.

Sorry for the confusion, but this truck is a 2007 4x4. The gears and master rebuild kits added up to 1200 for both ends. A friend has the skills and tools. I will be selling the 96 in my Sig.
3.55 and auto are good if you have a mystery switch. I would not tow without an exhaust brake. It will be the next purchase after fresh injectors. The 3rd gen brakes are so much better too.

1200 is worth the mod. I was expecting something in the 4k dollar range. Rear end work is not for the beginner. Common rail gen dodges are supperior to the old ones I have. Alot of electronic tunners available. Future plans to put 3rd gen brakes on my rigs. What is the mystery switch? Is that a torque converter lockup? Fresh injectors should be good for mileage. I too want an exhaust brake, especially on the auto.

yes the mystery switch is a 3 way control of TC lockup. 3 modes:
Stock behavior
No lockup ever
Manually locked

That last one can be dangerous, you need to deselect that before you stop.

I'm joining the diesel ranks again. Picked up an early 91 2WD auto W250 with 3.07 rear (I think) 135k showing nonfunctioning speedo odo at an auction. It need lots TLC and I'm a little nervous about the auto since it does have a 5th wheel ball mounted. Rotted floors, no headlights or heater control and a very leaky VE44 throttle shaft but great other than that! That auto is big mpg penalty, I know. I hope I can get high teens with it though. Love them inline 6s and 1st gens.

congrats! That should be no problem, more likely a solid 21 MPG at 55 or so.

What's the latest? LTX tires installed? Better idea of overall FE now?

I rarely drive the truck without the 5th wheel attached to it. When I do, I get 22 or so on freeway miles. It has been great with the new gears. I towed a 9000 pound forklift home on a 14K tilt trailer yesterday, and did not miss the lower gears at all. Granny does the trick off the line.
Still running M&S tires on it. I have some michelins on rims for the winter that are LTX.

Update on the truck:
I planned on overhauling the engine next winter. We knew it was on borrowed time when we purchased it.
Somebody foreclosed on the loan :P
Last week I started it up on a relatively cold morning, and she ran like crap. Sounded like 5 cylinders, smoking, vibration. Times up!
I drove it on my errand anyway, what could it hurt? It drove OK, and the only telltale was a little vibration.
On my way back home somebody rear ended me :D
Kick a guy while he is down........no damage done other than possibly the bumper itself, and it is hard to tell. It is not a virgin bumper.
So I drove it to my friend's place Monday about 100 miles away, who has the experience, knowledge, a lift, big shop and tools. Ran pretty good and the lie-o-meter stayed above 26 MPG most of the way there.
By that night I had drained all fluids, removed the drivelines, transfer case, transmission, clutch, bumper, core support and all the radiators and condensers and intercoolers.
We pulled the engine the next day and took it to my trusted rebuilder in Canada.
About the transmission: It had some nasty looking shards on the magnetic drain plug, and a decision was made to overhaul it.
The rebuilder I went with has both the early and late G56 transmissions in stock and he does not care which one I give him, so I am getting a late G56 with higher gear ratios throughout. OD went from .79 to .74

I resoldered some pins and made an additional ground for the cluster. Then I climbed underneath and cleaned and reseated the speed sender at the tranny and bingo I have consistant speedo and odo function again. I've just got one headlight to fix and the aircon goes to zero pressure when the compressor comes on as repairs other than painting.:thumbup:

The diesel beetle assists the Ram 1 ton truck:
http://i810.photobucket.com/albums/z...ps7nyy7cms.jpg

Went in there easily with an engine hoist.
Much more fun getting it out with a truck mounted crane. I met the overhauler half way.

http://i810.photobucket.com/albums/z...psfqdthugm.jpg

Shiny new overhaul late transmission.
http://i810.photobucket.com/albums/z...ps61tmtppd.jpg

What is the new and old rpms @60mph? 1)gear chang 2) trans swap?
---port match the ehxsost manafulld on both sides .
Wrap it ... I used the extra thick wrap 1.5 rolls for man +hot side ehxsost...
Exhaust Heat Wrap
And T3 Turbo Blanket..
Have the man. hot tanked (to de rust) and 2000°+ ceramic paint.
This dropped my under hood temps to under 200° can stop at the top of a 7mile grade pulling 1000°f EGT(wide open ) pop the hood and hold on to the man. With out 3rd degree burns. The wrap reduced my 1psi point by 100° (from 600° to 500° ) = more efficient turbo. This drop was an across the bord shift.

---
kafer65. I make the same recommended ehxsost mods for you...

Keep the after cooler. Add a late 1st gen inter cooler/ radiator (early 1st gen too small for intercoolers per dodge/ cummins) put the aftercooler on a separate radiator ( stock is engine coolent180° intake charge =15% reduction in power from un burned fule per Cummings )my late has 15% smaller injectors and the same 160hp /400tq only difference is injectors and IC Vs aftercooler

where did you source the paint?

Napa in Castle Rock, wa

You might look in the archives of Diesel Power Magazine, I remember reading an article about a 1st Gen Cummins that they purposely did all the work to make it more fuel efficient, and if I remember right, it was a stick shift and a dually at that but they took part of the duals off and used masking tape to tape the wheels smooth, I will see if I can find that article and hopefully post a link!

Well I just tried a google search and about 5 links down I found this!!!

http://ecomodder.com/forum/showthrea...mph-16106.html

With the new gears it was ~60 MPH at ~1750 RPM.
The OD ratio went from 0.79 to 0.74
This is a change of roughly 6.25%
This brings it down to ~1640 RPM
I use the ~ because the tachometers on these things are not precision instruments :D
So now I am below the peak torque of the standard cam.
I have a call in to the cam manufacturer to see what they say about peak torque.

Color me surprised..
07=1600 peek tork 24v 5.9
07.5=1500 peek tork 6.7
With your larger 33.83" tires vs31.73"
Taller gears 3.72/3.42 vs 3.55
Your spun up tighter 1750/1640 vs 1605 ( calculated including 5% extra for no lockup)
The difference is a.79/.74 vs .69 OD in the late 1st gen (91.5-93).
In my opinion your 1640 is perfect for 60mph. As the engine boogs down/lusing rpm the tork gos upto peek. Seeing as you are building a tow truck insted of a mileage monster. For me its 65mph that allows this drop to peek.

I run 30~31" tires 99% of the time.
I will be doing aero mods so a 65 MPH cruise will be do-able.

Sounds like you need the under/over drive box back to get back to target rpm . A 285/75 r17 Vs 235/85r16 is were i got the outside diameters from.
Edit : or is the rpm stated with the smaller tires?

It is! I have plenty of choices now.
One of the plusses of the new transmission is in gears 1~4. They are all a bit closer together now, which is nice for the shifts while towing. Often you get in a spot where you really have to rap out a gear to make a shift, so closing up that spacing by any amount is welcome.
The jump to OD being greater is not really an issue while towing. I won't use it on a hill, only on the flats or downhill. The OD gears are not as strong and when you run in them, it induces a side loading in the transmission that builds heat and wear. My rule of thumb is no more than 10 PSI of boost in 6th.

I have the engine back from the rebuilder. I will probably wrap the manifold and blanket the turbo. I took it apart and there is little to no port matching needed between turbo and manifold, just a minor cleanup of a casting ridge.
Looks like I will start engine re-assembly Wednesday next week, and get it ready to go by late Friday.

I put it back together over the last two days and started it this morning. After a short test drive and fixing a loose connector, I got the trailer ready, hooked on and towed it home through 90 miles of semi-crappy traffic.
The cam has made quite a difference. It builds boost at a much lower RPM now, the throttle response is much better. Where I used to kick out a chunk of smoke that was mostly but not all due to the rings, now there is a small puff. I am sure the new reman nozzles have something to do with that.
The cam is noisier at cruise. The engine sounds more like a VP44 24 valve now, with a distinct crackle that was suppressed by that timing overlap.
The rings did a great deal of breaking in during the initial cam break in. You run the engine at 1800 RPM for 20 minutes, and even after it warmed up we kept giving it less and less throttle to achieve the 1800. The Smarty Touch has pedal position as one of the options. IT started at 15% and dropped down to 5% by the time we were done.
As predicted 60 MPH is right at 1600 RPM with these tires. It is lugging with the trailer on with any grade, but rolls nicely on the flats and downhill. It shows a marked increase on the MPG gauge, but that is only for the "feels". I will do a proper observation after break in is done.

You could swap 88-95 balljoint Ford F-350 outers, knuckles, and brakes for a DIY free spin kit on the Dodge axle.

It is done already, and I retained the same brakes.

?Dose the smarty show EGT? What is it ?
Did tou do the wrap. Or are you getting a bace line first?
Are you using synthetic oil for brake-in , Trans ? Motor?
The mpg is up on a fresh engine. Awesome. It should climb as it gets closer to 50k mi .and things start to wear-in.

Smarty does egt with optional probe. I installed it but need to wire it.

I'd love to see 1600 at 60-mph for solo!

As is, the NV5600 6-speed man trans with stock tire size and standard 3.73 gearing I see 1625-rpm at 54-mph on the city freeways here in Fort Worth. (RPM is from Ultragauge OBD reader).

These trucks are set up to run and "work" 55-65/mph maximum, IMO.

As per the Dodge Owners Manual I've always used First to get it rolling. The shift to Second is almost instantaneous. (Normal rate of acceleration for one of these is best described as ponderous: it's a medium duty synchro trans behind a medium duty engine. Design life is far longer than the V8 diesel drivetrains, and this is part of the tradeoff). So when I've considered the 3.42 swap it was in the knowledge that I'd have to stay in the lower gears longer, and to a higher rpm before shifting to bring it back in above peak torque. Especially when loaded. (I've also used these trucks on the oilfield hauling 20k+ trailer and load; but in 4.11/DRW configuration ).

But these HPCR Cummins trucks are already overpowered straight from the factory for their intended use. So the "compromised gearing" vis-a-vis a decent load is more about better skills at the wheel to get up and go. Into traffic, across highways (I already avoid left hand turns solo, and REALLY hate them when with my trailer and stretched out to 63'; the trailer momentarily stops across all lanes in a left while it pivots; why trip planning is an FE requirement for working trucks, not optional), and down the highway entrance ramp. May take well over a mile to reach cruising speed.

So, FWIW, I spent nearly all this past year entering highways in my work truck at anywhere from 25-40/mph. It's just not a concern given some ability to read mirrors and interpret. It's why we have a wide differential between lower and upper speed limits.

For what the OP and I both want (I'll state it as better, full-er use of each gear plus a relatively low top end speed while working; relative to the moronic masses travel speed), it's a win. It'll take some adjustment as I've been driving this pickup about ten years now. I've wanted to do this gear change for several years but it's still not at the top of my long list.

I know I'll be in Direct more often, but Overdrive isn't a "strong" gear in the first place. Downshifting more often is a penalty offset by better flatland and solo MPG. Granted that as a commercial driver I don't give much thought to having to shift more often. Nor do I spend any time anymore in trying to improve MPG as the percentage gain on a stock truck is too small beyond my current efforts (I've experimented), so I know I'm ready for truck specification changes.

And those experiments in driving technique show me that I'll willingly (I hope it's also happily) compromise heaviest load towing ability as my truck and travel trailer are considered by me to be a matched pair. Their combined weight is less than those oilfield loads. Thus, not hard work for a Cummins.

I'm looking forward to what the OP has to say about the camshaft change with this gearing. (And as a note I can't always sign in depending where I am, but I always read the posts/threads).

Any plans for a data reader so to re-program on a custom basis?

.

After every one suggested NOT wrapping the manifold due to cracking problems in the late 3rd gen, I opted to leave it off. I did wire brush it and the turbo casting and elbow, and painted with high temp rustoleum . Only 8 bucks at Home Depot.
Engine has the usual Rotella T conventional oil. It will get changed out at 500 miles. The transmission has Lucas Oil 50W synthetic. Not too pleased with the transmission, it is quite notchy in R,1,2 in comparison to my old transmission. I hope the synchros break in some.
There is little break in left to do, in reality. There was virtually no oil consumption in the first 100 miles, and no visible blowby either at the tube or oil cap. Next time I start it up I will put a cork on the blowby and video the oil cap to show the totality of the blowby.
The rebuilder's recommendation was to go out with the trailer on and climb some hills :)
That's what I did, and the truck will sit until the next time I want to go out and camp. I think next weekend is out due to subfreezing temps, but I hope to go the following weekend. I am definitely champing at the bit but want to be practical about it.
Slowmover,
right now the wallet is sucked flat, so I will stay with what I have as far as instrumentation/tuning. The Smarty Touch I have will do UDC tuning but nobody has pursued it much since the advent of EFI Live.
The built in MPG gauge is quite confused, so all it is good for is to reset it often and see what different gear/speed combos do relative to each other. I sure wish we could calibrate that overhead!
I see a future with possibly less towing MPG, due to not being able to use OD as often. To amend that situation I will have to be diligent in upshifting whenever the opportunity arises.
All this changes with the future trailer design, which will have a lower CDA than the solo pickup :) , coupled with a target weight of less than 5000 pounds.
The engine will be able to handle a moderate grade at 1600 RPM with those lighter loadings.
Starting out in first, it has enough gear for most any situation with the trailer. In the extreme case I can crawl out of a bad spot in 2wd low.