Engine/Transmission (1998.5 - 2002) Loaded Question: 4x4 mpg vs Lock Out hubs

[John - K5AWO]

Just so you don't have to look at my signature, I have a '98 24V 1 ton dually 4x4 auto transmission. Great truck, dependable. It just likes to sip heavier on fuel than I wish to enjoy. The TQ has almost zero slip once the engine is over 1500 RPM. 93% SunCoast triple disc TQ. As a matter of reference, left idling and in drive, the truck on flat ground will upshift into 3rd and make 22-24 mph w/o touching the throttle.

I retired a year ago, finances are lining up to let me hook up to the 34' TT and start sight seeing.

So far, empty MPG is 12. 0 to 14. 0 if I am a good boy. Truck weighs 7,800 unloaded and about 35 gallons of fuel. It will hold 85 gal/fuel. With the TT hooked up, it gets 9 or 10ish on level ground. The TT weighs 7,700 empty before loading for trips. So, figure I will be about 15,000 ready for the road.

Question: Is it worth while to install Lockout Hubs on this truck? Will the possible improvement in MPG ever pay for itself?

I will never be driving huge distances in a given year, I speculate the standard 10,000/year might be all it does. The truck has 134,000 miles on it now.

I am satisfied with the way it runs now, but am wondering if a bigger exhaust would help EGTs and MPG? maybe a larger turbo if the one I have gets tired? I never push it harder than 27-28 psi.

 

[EDankievitch]

You have the central axle disconnect you will not see much of as gain as the newer trucks that don't have any disconnect. Biggest thing hurting your unloaded mpg is your 4. 11 gears. The 3. 55 's would give you better but you'd loose some when towing in the hills.

 

[HBarlow]

Larger exhaust won't do anything but lighten your wallet and a bigger turbo would probably cause drivability or performance issues. A turbo is carefully matched with injectors and other factors. Choosing another one off the shelf would probably not be a good idea unless you're an engineer at Cummins, Caterpillar, etc.

 

[Grizzly]

I've done some research on installing Lockout Hubs on my 05 and have come to the conclusion that it is not cost effective for my particular needs, I believe you'd have to tow a lot more miles to make it cost effective for you also.



george

 

[Road Dog]

Your biggest gain would come from a computer set to a mild hp increase. I pick up a couple of mpg from stock to TOW mode. A turbo would bring down your exhaust temps but not offer much in performance without other mods.

I disagree with Harvey -- turbo selection trades off volume (how much air it moves) and spooling (how fast it spins up). Dodge tends to go with faster throttle response (spooling) and cost. As long as you're honest with yourself about your needs it's not rocket science. There's a couple that get good reviews: BD's Super B Turbo or PDR's Super 300 (they're both in my neighbourhood).

 

[WILLD420]

I have a 2002 2500 4x4 with a built 47re, 3. 55 gears and a 1st generation suncoast t/c that stalls about 1950 rpm with 255/85/16 Toyo's. It is lifted 5" and has a huge Ranch hand bumper on the front with a winch and all kinds of weight adding goodies that push as much air as a barn going down the road. Empty I manage 14-15 on short trips around town and such, on a trip to Kansas this year I averaged 14. 8-15. 5 with the cruise set at 84 across I-80 using a set of highway tread 235/85/16's. On a recent trip to Tucson, I averaged 16. 4-17. 8 per tank cruising at 7 mph over the posted speed limit all the way with the 255 toyos.

I have run 235/16 tires all the way to 315/16's and not noticed a great deal of difference in the mpg area, but a huge difference in towing power. I have an Edge w/Attitude programmer and a bigger turbo (HX-35/40), otherwise the engine is stock. I gained 1-2 mpg towing by ditching the stock turbo, I also dropped about 300 deg egt just by the turbo change. With the stock HY-35 turbo, I could hit 1250-1300 deg egt on the stock setting on the slightest hill, at 1/2 throttle or a little less towing our 12K lb 37' 5th wheel at any elevation from 4000-8500 ft.

I see that you are running RV275's so you definitely have more fueling than I do on my stock setting, since I have the original injectors. I would be surprised if your egt's are controllable once you head into any type of mountains with any elevation at all.

I doubt changing to the free wheeling hubs would gain more than 1 to 1. 5 mpg, since that's about what they average in all of the write-ups and magazine articles I see. I definitely don't think they are worth the 1500-2200 dollar price tag for someone who only goes 10-15K miles per year. If you kept the truck another 10 years, that's only 100-150K miles. A set of stock unit bearings should last that long and at $400-550/set, that's a lot of fuel you can buy for the difference.

Are you running a fuel additive? I have tried several and I find anywhere from 0 mpg gain, to 1. 5 mpg gain depending on the additive. My last bottle was Redline and it seemed to pick up about 1/2-1 mpg cruising empty on a long trip. Might have been a tail-wind or just a good batch of fuel, but it lasted 3 tank fulls, so I don't think it was an anomaly.

Don't listen to people who tell you that you need to be an engineer to modify your rig. You obviously know a little judging by the quality modifications you've made so far.

A mileage type programmer, a better turbo and keeping your speed down will add what you are looking for. If I hold 50 mph on level ground, I can break 20 mpg empty, but I get bored really fast. At 84 mph I drop 5 mpg empty. Towing at 65 mph in drive I get about 10. 2-11. 8 mpg on trips across the middle of Nevada, toward the high end if it's all flat. As low as 8 mpg if I hammer down and run 80 with the trailer on the back. *(Yes, I realize some will say that's 20 mph too fast, but they are usually the ones I pass. )

Hope this helps a little.

 

[John - K5AWO]

Sorry guys about not getting back to you on this thread. Had the flu or something running through the house. Lots of sick folks here.

I am still doing the heaves.

You all have given me some good solid advice that I need to mull over. For right now, it sounds like what I have is pretty good "all around". When I get my senses back in order, will rethink all of this and revive the thread then.

Thank you very much,
John

 

[SRath]

But when you pass another dodge sitting with a front wheel jammed up into its wheelwell, and a huge towing and on-the-road repair bill ahead of it from the failure of yet another unitized hub, you would never again ask if the conversion to lockouts, with the accompanying live bearing spindles, was worth the investment...



just more food for thought...



I can only imagine what a unitized hub failure with a 5th wheel and 7% downgrade would be like. Not much better than the inevitable brake failure that dodge designed into these trucks with their use of ultra-super-cheap rust-prone brake lines.



With either "manufacturer cost saving" item, it isn't a matter of "if"; only "when".

 

[John - K5AWO]

But when you pass another dodge sitting with a front wheel jammed up into its wheelwell, and a huge towing and on-the-road repair bill ahead of it from the failure of yet another unitized hub, you would never again ask if the conversion to lockouts, with the accompanying live bearing spindles, was worth the investment...

just more food for thought...

I can only imagine what a unitized hub failure with a 5th wheel and 7% downgrade would be like. Not much better than the inevitable brake failure that dodge designed into these trucks with their use of ultra-super-cheap rust-prone brake lines.

With either "manufacturer cost saving" item, it isn't a matter of "if"; only "when".

Oh, you guys have already talked me out of changing the hubs. I am going to stay with the OEM axle parts. So, in that essense then, this thread is indeed finished.

I was thinking of the rest of the stuff that was brought up in this thread. I will capture all the posts into a document and mull that stuff over later.

So, again, thank you all for making it abundantly clear that unitized hubs aren't the Cat's Meow...

Besides, when it is nasty, cold, and sloggy on the ground, just reaching down for that 4x4 lever has a lot to be said for it :-laf

John

 

[RAJohnson]

I have a six speed. But in the past I had a 95 Auto with 4:10 gears. I put on a Aux transmission made by Gearvender and milage increased quite a bit. If I remember right I was getting 16mpg pulling my trailer about the same size or weight as yours, with the 95. When I sold the 95, I switched it over to the 02 and now get 22 around town and 24ish empty on the hi-way. Pulling runs between 16-19mpg. There a bit pricey now but if you plan on keeping the truck or at least switching it to a different truck in the future if needed, there worth it. Exhaust temp gauge is a must so you dont lug it to much. When it was on the 95 which had a Auto, I had to call the factory and let them know I would not hold them responsible for tranmission failure if they would tell me how to get it to spilt over the factory overdrive. They were worried about a person smoking the torque converter. Its fine if you drive by gauges, EGT, Boost, RPM.

 

[WILLD420]

I have my original unit bearings for spares, I throw one in the trailer in case I ever have a failure on a trip.

I also check for play in the bearings every 5K at oil changes. I'm sure there have been failures that come out of nowhere, but I would hope a little warning would come before a failure. My originals had 120K on them and were still nice and tight when I put on new ones for my sanity. I have heard of failures from 40K to 250K so I think it's anybody's guess when one will go. I also think how the truck is used has a lot to do with the failures. Most of the ones I've heard of that failed early on, were abused with heavy loads and driving through water crossings a lot.

I also think quality of the bearings have a lot to do with their life. I bought USA made Napa bearings, but I've seen SKF(Chinese) for sale a LOT cheaper on Ebay and elsewhere.

 

[SRath]

I did Mark's very clever greaseable unit hub mod on mine until I get the rest of my 35-spline (like a real dana 60) shafts, hubs, spindles and ultra-reliable lockouts, dual piston calipers, etc gathered up.



I can now grease them, but I'll never trust them or miss them when the day comes I can use them for throwline anchors.

 

[John - K5AWO]

Hey, thanks for the extra info thrown in here. Very useful.

I do not abuse my truck, not even close. I worked hard for my money and have never had enough of it to not feel extreme pain when something breaks.

Full gauges, and watch them like a hawk. Never let the EGT get over 1200, in fact, 1100 starts to make me nervous.

Most of the time, the turbo boost is running 5-9 psi. When the EGTs get up to 1200 and I'm pulling a hill with a load, I get out of the OD fast, and let the engine wind up some more to try and hold 55 mph. That usually has the boost up at 27 psi, which seems to drops the EGTs down about 200 degrees or more. Depending on the grade of course.

I used to have a Gearvender on a Suburban. sure do miss that thing. That would probably be a better thing to install than messing with wheels/tires. About the same cost. maybe I could find one used.


RAJohnson, I really appreciate your input on the MPG figures with the Gearvendor. gives me some real world numbers to throw around.

Thanks all,
sure love TDR... .

 

[JMcCoy]

I changed over to Ford hubs for the reliability of servicable bearings, better brakes, and most importantly the free spin option. I wanted the free spin option so I can run a locker up front for true 4wd. Oh yeah, to get rid of that POS CAD. I would not do it for the fuel and service savings. It would take too long to recover. Since I had the CAD Dana, I only see . 5 to 1 mpg increase. You might see more without the CAD.



You should be getting better fuel milage than what you are getting. I would definately go for some sort of a computer module to adjust fuel/timing for your driving conditions. An OD unit would be nice for drivability reasons. Again, it would take too long to recover any cost. Just my . 02. Good luck.

 

[Regcabguy]

If I had the dough I'd get the Dynalocs. My friend's got them on his '05. Driving effort is reduced and all that rotational mass is shutdown up front.



When you look at the replacement costs of front hubs, u-joints and the associated labor it's worth it.



On the mileage: he's getting maybe 1 mpg more.

 

[Cosmo]

Larger exhaust won't do anything but lighten your wallet and a bigger turbo would probably cause drivability or performance issues. A turbo is carefully matched with injectors and other factors. Choosing another one off the shelf would probably not be a good idea unless you're an engineer at Cummins, Caterpillar, etc.

Once again, Harvey is talking out his buttocks.



What size is your exhaust, from the turbo back? IIRC older trucks had 3", which I think is a bit small for a turbocharged near-6 liter truck. 4" seems to be the magic number for up to about 500 hp, beyond that you would see better gains with larger.



Anyway, your unloaded fuel economy seems dismal. Is that because your driving has a LOT of stop and go? I'm not all that familiar with dual rear wheel trucks (but I'm contemplating getting one) but similar trucks with single rear wheels can and do get high teens regularly, and low 20's with manual transmissions.



I would wager that opening up your exhaust a bit and getting a programmer to alter your engine tune will really wake your truck up and I bet you'll see an improvement at the pump too.



However, being a VP44 truck, I'd make sure you've got a GOOD lift pump solution and make sure you're monitoring EGT, boost, and your trans temps.

 

[dclassens]

Harvey is 100% correct... .



Harvey, Sometimes I just love the NEW TDR crowd like Cosmo. Like Harv, I have been on TDR for a decade or so, and all the dead horse beatings I have seen just make me smile. The original poster makes known up front that his truck is an auto and Cosmo rattles on and on about aftermarket parts and pieces that will never pay back the invisible fuel gain he is referring to, especially on an automatic truck. After owning 10 dodge trucks I think factory settings with upgrades to improve life span, NOT power is the only way to make real life sense out of owning these trucks.



John - K5AWO, like you last post said, keep it simple and don't try to reinvent the wheel like many others here are trying to do. Dodge truck may be upgraded but not to save money.

 

[HBarlow]

Harvey is 100% correct... .

Harvey, Sometimes I just love the NEW TDR crowd like Cosmo. Like Harv, I have been on TDR for a decade or so, and all the dead horse beatings I have seen just make me smile. The original poster makes known up front that his truck is an auto and Cosmo rattles on and on about aftermarket parts and pieces that will never pay back the invisible fuel gain he is referring to, especially on an automatic truck. After owning 10 dodge trucks I think factory settings with upgrades to improve life span, NOT power is the only way to make real life sense out of owning these trucks.

John - K5AWO, like you last post said, keep it simple and don't try to reinvent the wheel like many others here are trying to do. Dodge truck may be upgraded but not to save money.

Yeah, me too.

Anyone with a keyboard can be an automotive or petroleum engineer. They show up here from time to time running off at the mouth like cosmo does but after awhile they disappear, probably tol move to one of the other websites where their ideas and opinions are common.

 

[cerberusiam]

The original poster makes known up front that his truck is an auto and Cosmo rattles on and on about aftermarket parts and pieces that will never pay back the invisible fuel gain he is referring to, especially on an automatic truck.

Well, it is an automatic truck. You did get that much right.



Lessee, the OP had upgraded injectors, a performance box, upgraded transmission, likely upgraded LP and and IP, upgraded exhaust manifold. About all he hasn't upgraded is the turbo and exhaust. Following a well documneted and established blue print for a balance of power\efficiency it would seem those items would be next up.



Since the injectors, pump, exhaust manifold have been changed then it would make sense, per Harvey's suggestion, that a turbo and exhaust better matched to all those pieces would be beneficial. Possibly a CAI of some type if the OP doesn't have one would also benefit. Maybe not a BIGGER turbo, but there is sure a BETTER turbo available than a stock HX35.



I would have to agree with the majority on a turbo and exhaust as next steps. The lockout hubs are a nice addition but purely for mileage concerns the OP isn't driving enough to warrant it. Pulling a TT is not going to be hard use so the unitized hubs are viable to 150k or better in that type of scenario. A turbo\exhaust would provide much more ROI and enhancments for a stepped up towing regimen.



I don't see a whole lot wrong with Cosmo's statements or reasoning. I would have to agree with him on several points:



1. The OP's empty mpg does seem low.



2. Harvey does in fact talk out his buttocks on occasion.









:-laf

 

[dclassens]

No matter how you cut it, the most accurate post throughout this thread is Harvey's. The best thing about TDR is that when you post a question, the answers are related to exactly what you are looking for. I enjoy this site and hope it remains a great resource for keeping these trucks going, not a site about guys fooling around and blowing up their transmissions and unrealistic data about diesel engines and drive trains.