I believe if I lowered my RPM I could improve my Fuel Economy significantly. I can't install an overdrive cause I have a water tank I installed under my truck that would interfere. I have looked into taller tires but currently if you get taller tires you also get significantly fatter tires so any economy gained from the lower RPM from taller tires is offset by additional rolling resistance. I have a 6th gear that is 0.79 and understand I might be able to get a 0.73. (I have a 6 sp manuel) Is there anyway I can get a lower number than 0.73 for my trans? Also is there any way I could get a lower number for my first gear? (If I got a lower number for my differential it might be nice to use 1st gear instead of starting in 2nd gear and I never tow so a lower number would be no problem in that regard) My Differential is a 3.73 and I understand I can get a 3.42. Is there any way I can get a lower number for my differential?

 

May I suggest to lowering your speed not to exceed 1700 rpm....if you have the time. Case in point. I have a 5.9 ISB Cummins 275HP, 660 ft/lbs with an edge enhancer with 40 more HP, 38 foot motorhome, towing a jeep to the Moab, UT Jeep Safari. Total weight about 30000# gross. Since max torgue is rated at 1600 rpm and 1700 rpm is 55 mph I tested it driving for 4 days (one way so far). I found for each day to drive the "usual distance" it took me an hour and a half longer than usual. By doing so I increased my mpg from 9.8 to 11.6-12.3 mpg. By taking the extra time I "paid myself" the extra time in savings of fuel by 15%. I figure I will spend roughly $1400 in fuel for this round trip. It would have otherwise cost about $200 dollars more in fuel (driving as usual) or about $25 per day of driving for doing nothing more than be willing to be passed up and in doing so paying yourself $25 dollars a day for the extra time spent driving...you would have to earn $35 dollars in order for you to be able to spend $25...thus saving even more money. IMHO it can really add up! Pay youself to be passed up!!!

Believe me, as I drove I remember seeing the same people passing me up....how much fuel did they save?

 

With a taller gearing such as 3.42 or higher you hit a point that fuel mileage dosen't increase but even might decrease.Your pushing a lot of weight and goes through air like a brick. 3.42 gear might get you 1 to 2 mpg more.Thats all thats posted after a change to 3.42.

 

your truck has a sweet spot at about 1800 rpm or about 60 mph; listen to halftrek. past that get a smarty jr ,5"turbo back, cfm+, and heater delete spacer. these will cost a lot less than the gear change and gain a lot more mpg. learn to drive your truck like it was a big truck , allways start out in 1'st excelerate slowly match rpm in gear change down shift when coming to stop it will get easy to do and the driving habbits will improve mileage and extend the life of clutch and pads considerbaly, i cant' spell

 

on the 03 quad cab single wheel 3500 dad gets 15 running around back country roads, 18-19 at 70 mph and at 55-60 mph it jumps to the 21 area.

 

Carl48: What is a 5"turbo back, cfm+ and heater delete spacer?

 

5" turbo back is exhaust that is 5" diameter

CFM+ is the air intake tube from the cooler to the head, search ebay for cfm+. The stock one is cast aluminum which your dipstick bolts to. Aftermarket ones have less restriction and more importantly have larger area.

Heater Delete is buying a spacer to remove the intake heater which bolts to the intake tube. You can run this 8 months out of the year but if you live in cold climate, I would put back in for the winter months.