Bill W.

A side note. I hope you don't mind my jibes about fairytale mileage and automatics. I would really like to experience a 24 mpg drive but it hasn't happened yet and my rig is pretty stock engine wise. Maybe a HO just can't do it. BW

Hi Moses. I'll go straight to it, 494.5 miles, 23.83 gallons (FULL, just like when I started) yield 20.7511 MPG! Details. 03 HO. NV 5400. Tire pressure 74F, 64R, Toyo 295/70-17 MT, dia 33.5". Speedo recalibrated and accurate. Final drive 3.73. I used the cruise control as much as possible set at 64, tach about 1800ish, tried hard to shift near 1600. Only juiced it a couple of times. I also have a Peragon bed cover and the former owner put a front leveling kit on. There has always been a bed cover on since I have owner it so my variables are consistent, including the Detroit Locker. I am pleased with my results especially with the grades. A couple more notes. EGT on flat road was in the 400-600 range, boost in the 5 range. I had very few times when the boost would go to 0 like coming downhill E to Truckee. Sometimes it would still be on 2-3. I found that odd because we were coasting in 6th. Due to the SB intake elbow? The boost and EGT are new mechanical Autometer gauges also. I also think my thermocouple is failing because at a roadside stop near Truckee, in the 40s out, EGT stayed on 400 for quite a while. Probe is after turbo. I bought this rig in Portland OR with 110k miles on it. The former owner had a 40' camp trailer, a four horse trailer and a boat he would pull w it. He put a Banks Six Shooter module on and it worked! However, not legal in CA. I found a business in the Sierras that was liquidating his stock of CA legal Banks units so got one. It doesn't work unless you really put your foot in it and have it turned up to 6. Because it doesn't work for me, I leave it on 1 and could take it out and not miss it. I rarely pull a trailer. I will be going to Thunder Hill raceway on Memorial Day for a car event and pulling a trailer then. It is the same place I went to and wrote about in our June '23 exchange. I'll find out if I have a headwind again and see what kind of MPG I get. I went back to the beginning of this thread and scanned through it to refresh my memory. There are some good points in here and when I get a moment I will dig into them. One of which is your tuner unit. If it is CA legal then I would read up on it. Sincerely, Bill W.

Forgot to mention I am using a red high temp grease. Don't recall the brand right off. I'll post it when I get the MPG results from this next trip..

Hollo, Moses. I had to chuckle to myself that there have not been any more posts on this subject since our last exchange. Who knows, maybe most don't care about getting the best mileage that they could get. For me it is a challenge! I like to know what my best MPG is and if I choose to live large, then I see how much the effects are. I just wanted to let you know since I have adjusted the Spyntech Hubs from the torqued method to the free play method as we have discussed, I am taking my first road trip since last year where I can check my mileage with the new wheel bearing adjustment and also with the SB intake elbow. As before in my tests, I will try to keep all the variables constant so I may prove to myself a true outcome. My around town and very short trips in the Bay Area have been consistent with MPG results in the 14-19 range, depending. I am going for the fabled mileage of 22-24 range that so many boast about with big tires, 70-80 MPH 4.11 final drive and ??? what else can I throw in? Automatic? My wife and I are going to Nevada City, Virginia City ,Lake Tahoe and then home. Back to work on Friday. I will post my mileage when we return. Sincerely, Bill W.

Update, with the wheels installed i felt there was too much free play and my conscience got the better of me. I have always adjusted the front axle bearings in a similar fashion on all of my rigs as we are discussing and never gave it a second thought but in this case I decided to give it another go. I had not noticed in the past that the outer nut when torqued will make a difference on the free play but when you mentioned it, sure enough it does! So because the holed washer barely makes a difference no matter which side is in, I painstakingly adjusted the bearings with the wheels on so I barely feel any movement. IDK what the endplay is now but going by feel I am much happier. If you care, I will post my findings at a later date. Bill W.

Hello Moses, I hope you had a good Fourth of July! I finally made time to check my front hub bearings. Both sides had no endplay but I found the left side was tighter than the right. To be sure I had followed the Spyn Tec directions I dug them out. I couldn't find anything on line to cut and paste so below is their print transcribed applicable to the bearing adjustment method. "Thread the inner spindle nut onto the spindle. Using a spindle nut socket and torque wrench, tighten the spindle nut to 50ft-lbs. Do not over tighten the nut. Rotate hub back and forth while tightening. Back off the spindle nut 1/4 turn. Slide on the lock washer. Make sure the pin is aligned with a hole on the nut. Thread the outer nut onto the spindle and torque to 125-150 ft-lbs." That is what I did. In order to get the pins to line up, rather than loosening the assy, I went tighter. That, I'm sure is why the L side was tighter than the R. So now I set the free play as discussed. Using a dial indicator, I now have .006 on the L and .004 on the R, brake pads backed off, no wheel on. The holed locking washer does not allow micro adjustment if it is turn over. I think what I will do is go back in and snug them up one hole because with the wheel on, there is more free play movement. In any case, I am hopeful it will make a slight improvement on my mileage! I have been reading Dodge and Cummins forums about EGT, boost, RPM and MPH and the claims of the related info are all over the map. Those clowns just thrown out figures but did they really make accurate observations and write it down? I doubt it but if it is on the internet it must be true. Only one or two postings said slow down! If I were to drive at 80 and 2400 RPM, my mileage drops to 14-15 or lower. I know because I did it on Hwy 95 through Nevada. Those numbers are relative because it was a while ago. So, in order to determine if I will have an increase, the next time I am able to check I will try to duplicate the same driving conditions of no more than 1900 RPM and keeping my speed around 67-68 or less. In the end I am very happy with my rig and it beats the hell out of my former Ford with the 460 for mileage. Bill W.

Hello Moses, I have a mpg result for my last trip but must first start with a preface. I am not a science nerd, anal control freak. I have pretty good records of my past mpg and since I was testing one specific part to see if there was a difference, I had to control what I could and list those things for this posting. On this trip I did verify the accuracy of the odo and it is extremely accurate. One thing I don't wave any records for is I changed to the SB intake at the same time I replaced the mechanical EGT and boost gauges with a different brand of mechanical gauges. I have a memory of what those gauges indicated before the switch but had nothing written down. It would have been nice to have those numbers to compare. Oh well. Controlled items. Tank fill up was done in the same fashion before the trip and after. FULL! Rig was empty and I have a Peragon bed cover. Cool weather, no AC and windows up. Tire pressures 72f, 62r. I used cruise control almost the whole way for consistency with rpm and speed. I did have a couple of occasions where I had to accelerate rapidly up to 80 for 30 seconds but coasted back to cruise. Posted speed limit was 65 and 70mph. About 160 miles of the 266 mile trip was during the 70 limit. Indicated rpm of 1825 was 64mph. 1900rpm was 67-68. I wanted to keep the rpm below 2000. I did about 5 miles of slow moving with traffic and stop lights. The road was mostly flat the whole way, no hills. Boost gauge indicated 5-10psi, mostly at 7. EGT was 400-600F, mostly 500. Out of my control, on the way home there was a MEAN headwind. 265.8 miles, 13.506 gallons, 19.680mpg. Conclusion: No noticeable improvement for mpg during cruise at highway speeds with SB intake elbow on this trip. I did not try to see if the engine spools quicker or any other HiPo tricks. I have nothing to measure or compare it to. However, I did notice as soon as I put it on and with my other short drives prior to and during this trip, the EGT cooldown is faster before shutdown. Next I will check the front hub bearings for preload and adjust as we have discussed. If still preloaded, I expect to measure a difference in mpg there. I'll post my findings here. Bill

Hello Moses, I hope all is well with you and your school is taking off. I have been very busy with life so have been laying low. I just wanted to tell you I will be taking a short trip of about 300-400 miles on Memorial Day so will be checking my mileage with the new SB intake elbow, I have also been thinking about our last conversations about setting the front wheel bearing torque by feel as we had discussed. I will do that after I get results for my drive first. Of course I will post my findings here. Did you get the free wheel hubs from Spyn Tec? Bill W.

Moses, for the hubs I followed SpynTec's suggested method of preload. (Torqued). Perhaps that is why I didn't detect much of an improvement to my mpg. Supplied with Timken bearings, I did check the hubs for heat after a long drive when I first installed them using my hand but did not detect anything unusual. Maybe now that the bearings have run in, I will readjust them to have .002 or so free play and see if that makes a difference. But not until I get mpg results from the intake elbow. The RH lower ball jt was very loose, shot, and the LH upper was marginal. The right side is where the unit bearing had failed as well as the u joint. it was literally coming apart. Non greaseable factory u jts. I went back with Spicer non greaseable. The upper Dynatrac ball jts are greaseable but I don't remember if nor can see the lower ones. I think they are and require a needle. I haven't had to grease them yet. Will look it up when the time comes. Bill

Good morning Moses. This reply is in the same order as my original post so it will have some continuity. The NV5600 transmission is a beast for sure. Weighing nearly 400LBS, one must be prepared to remove it. The gear ratios are very evenly spaced and I have never wished one was a little lower or a little higher while going through them. It is a little difficult to shift however. Finding the gates, learning the springs in the shifter, and the exact lever travel took me a little practice and I sometimes still have trouble. Once in a while I get a little gear clash but mostly when cold. It cannot be shifted fast at all and would never win in a drag race. I didn't buy my rig to go fast. I have other toys for that. I have no personal knowledge of the G56 but from what I have read, its tow rating is lower and when subjected to heavy loads the aluminum case has a tendency to spread causing cracks or breakage. A steel girdle can be fitted to help stiffen it but I don't know of the effectivity. It is probably a good transmission that shifts easily and precisely and works well for a daily driver and light duty use. You may be better off with the 7 speed! I have no regrets converting to free spin front hubs. Since I was facing a forced decision in a replacement, I wanted to spend good money once and have a serviceable hub rather than continue with the unit bearing and a chance to increase my mpg. In just about everything I do, I research, evaluate, consider the cost and make a decision. I chose SpynTec and used Mile Marker stainless steel hub locks. The SpynTec hubs are a quality piece and came with a very durable plating that shows no sign of rust since I installed them in 2017. I went with MM instead of Warn because of the cost. So far in their limited use I haven't had any trouble with the MM. In getting the knuckles apart and changing the ball joints, I couldn't find anyone that had a ball joint press to rent or the other tools required so I bought OTC kit 8031. An unexpected expense but I still came out ahead since I did all my own work. As for ball joints I went with Dynatrac. Carli makes some nice ones also but more expensive. I would warn other readers to make due diligence on replacement ball joints. I stayed away from Moog, Napa and another I can't remember because some are oversized or knurled and when they wear out... good luck. The Dynatracs are also rebuildable. Now I have an all new front end including U-joints. I would be interested if you find better braking with the hubs as I did. I am well aware of automatic locking differential behavior. I have a couple of cars with them and my '79 Ford with the 460 had a locker in the back. It was a purpose built rig and a wheeling machine. A lot of fun! My Dodge is not a wheeling machine and I did not buy it for that. If I had the factory posi I would not have changed it, I don't think. But since it was open and I had been in several situations where I had to engage the front just for an easy task where my Ford would march on without missing a beat, I went with what I could afford and a proven brand. All of my lockers are Detroit. Did you look for the ID sticker in your glove box for the diff gear ratio? Just curious. Hearing about your idea for the school is very interesting. Especially for differentials, I believe the tooling is a big obstacle for most including me. Torqueing the ring gear bolts on the AMM 11.5 was tough! I had my wife put the trans in first gear low range to keep the ring gear from turning while I torqued the bolts. Anyway, I will look for the notification of the launch date. And I will look at the site. Lastly the tires. I may have to resign myself to stay with the same size I already have of 295/70-17 and drone along at 65. Unfortunately when I see other Dodge diesels with bigger tires and ask them what they think and mileage etc, not many have specific mpg reports. Either the lie-o-meter or a best guess. Since this thread is about mpg, I want to be able to report back with my accurate findings for the benefit of others seeking the same. Thank God for cruise control. All the best, Bill

Hello, Mr. Ludel...I am pleased this post is still open for replies and I hope this goes through. I have a few things to share with you about my own experiences with my pickup and my continued quest to get the best mpg I can. I am the second owner of my 2003 Dodge 2500 crew cab SLT 4x4, NV5600 with short bed and HO 305 hp motor. I bought it in 2016 with 110k miles. The first owner took excellent care of it and kept 98% of the receipts, one of the reasons I bought it. Regarding this mpg thread, he did a few mods to it like put on a front leveling kit, Banks Six Gun module, Air Raid cold air box/filter and Toyo 10 ply 295/70-17 tires since he pulled a four horse trailer. My primary reason for buying this Dodge was the excellent condition it was in, the Cummins engine and getting better mileage than my former Ford with a 460 at 10 mpg. The former owner is a wealthy man and when I asked him what kind of mileage he got he didn’t really know. No matter, I drove it from Portland OR to the Bay Area on I-5 and got 19mpg, calculated by hand. I was way happy! Since then I have always been mindful of my driving antics, mostly trying to get the best mileage I could. Reading here, I never considered checking the odo for accuracy but it appears to be correct. The previous owner had the speedo recalibrated to the new tire diameter and it also appears correct. The best mpg I have been able to achieve to date was 23. I too have noticed if my rpm is above 2000 my mpg will go down about the same rate the speedo goes up. Going through Nevada with 70-80 posted limits, my mpg will be 14. If I keep the speed at 65, 2000ish rpm, I will be 19-21, all factors considered. I don’t rely on the lie-o-meter ever other than a trend. I always calculate by hand, every fill up. I have a boost gauge and egt gauge. I monitor them while on grades especially. Previous owner warned me of pulling a grade with a trailer in sixth gear, not so much for egt but for the trans itself. Just like you, I shift to fifth direct. Researching it, sure enough he was right. An oiling idiosyncrasy inherent in the design. There are fixes for it and I have accomplished them but I still shift down. One thing I noticed in this entire thread is no mention of tire pressure. An easy thing to overlook if one is not a real gearhead but it makes a difference. I have fiddled with this in search of a better ride with 10 ply tires only to the detriment of mpg. Back up to 70psi front and 60psi rear, and mpg returned. New Monroe Magnum 60s in the rear and my bounce was under control. Cheaply too. About 2000 miles after getting the truck, the RH unit bearing failed. In an effort to increase mpg, I decided to replace them with free spin hubs. Alas, there was not much of an increase that I could tell. If I were extremely disciplined and had a detailed log before the change to compare to after, it may be more apparent. Being like most drivers, that was not me. There are two redeeming factors though. While backing a trailer I use low range so i don't have to slip the clutch so much and if I have to turn full lock, I don't have the knuckle bump of the u-joints. The second thing is there is a noticeable improvement in braking. Reasoning if the braking is better the mpg would be better and it probably is a small amount. I am still happy I made the change though. Now I can service the bearings. and the hubs can carry more load more evenly. Important for rigs with more positive offset wheels which I don't have. Using your excellent article/ pictorial on the gear change in your rig, I used it for guidance on replacing my open differential with a Detroit Locker this past July. Thank you, for it as it helped tremendously! I like lockers even if I may suffer a little lower mileage. I have not been able to take a 700 mile or so trip to see if it affected my mpg but my shorter trips like to Tahoe and back are comparable to before. Tire pressure and tire diameter is important with a locker. I’m on it. For what it’s worth, when I bought my rig I sent Dodge my vin to find out if it had a limited slip. I also asked if there was a data plate or sticker/ tag anywhere. Turns out there is a sticker located in the glove box, at least on mine. Check yours. No tag on my diff housing. Incidentally my gear ratio is 3.73. I have read much controversy on this but in my continued quest to improve my mpg, I just bought a S&B intake elbow. This was not a pre planned purchase. Rather an excuse since I was replacing the Banks electrical boost gauge with an Autometer mechanical and I needed a place to plumb the gauge. A very nice piece with metal gaskets, boot, clamp and hardware. Smooth radius and no restriction like the OEM piece, logic says it should help. I did some simple math with a force, area, pressure formula based on the ID in comparison of the two and it calculates favorably. I have just finished this and have not driven anywhere other than down the street so no data yet. I hope to get lower egts while driving and a faster cool down before shutting down at minimum. There may even be a slight increase in boost pressure and sooner spooling with it. To be determined. The last thing I wanted to mention is I was considering going to a little taller tire in order to lower the rpms at speed. 65 is about as fast as I can go and stay below 2000rpm. The boost gauge is about 10 at that speed. I’ll have to double check. The Toyo tires on it are about 33” I was thinking about a 34-35” tire. I have not done the math for rpm yet but wanted to quiz you again that you thought your own motor was under too much load and therefore required more boost to overcome drag and load? If I could get a comfortable rpm below 2000 at 70 I think I would be happy. I read on another post on your site that another fellow , Steve Atkins, changed to 3.54 gear ratio and had a dramatic improvement with a second gen. I'm not going to change ratios, just tire diameter. Looking fwd to your reply. Thanks again for ALL of your work and publications! Bill W.