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Fuel mileage with 7.3L & 4:10 rear end

6K views 13 replies 9 participants last post by  DENNY 
#1 ·
Hi everyone,
I wanted to get some opinions on what most you all are getting good for fuel mileage on the 7.3's with 4:10 rear end.
I have a 99 7.3 4x4 auto super crew with heavy dove tail flat bed 244k on truck, 100k on tranny.
I have had it for 5 years. New factory transmission installed with purchase. I have never gotten more than 12mpg out of this truck. Runs same loaded down or empty. I have replaced right front caliper 3x in 5 years and brake lines 2x in 5 years. Both hub assemblies have been replaced in last two years.
I appreciate the input.
 
#2 ·
Any modifications?


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#7 ·
Those aren't big enough for these.

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#4 ·
I am getting high 16s at 75mph, 15s above 80mph. Read my sig for mods.
 
#5 ·
I have 410 gears as well and I average 13 hand calculated @ 75 mph most of the time. Very little in town driving. I've hit 15 but thats keeping it under 2k or roughly 63 mph.
 
#6 ·
Is your truck a Dually or SRW ?
 
#8 ·
I would toss in a 6637 and call it a day. Lol

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#9 ·
Do a 6637 intake filter. It is a very easy diy mod. Get more air in for sure then work towards a bigger exaust system and a obdii port tuner all very easy and you will see decent gains. Sound like you may be starving the engine for air. All the 7.3s I have had those are the three biggest bang for the buck mods if you want to keep it simple. If you want to go crazy im sure there is plenty of help on here for that!!!
 
#10 ·
Yes, I get the same, 12 mpg.
 
#11 ·
My '01 with 4.10's gets 13 empty and 9 pulling anything, including at 27,500 lbs with my old 3 car trailer and 2 RV's loaded up. Truck is stock as far as the drivetrain.
 
#12 ·
Its all about the engine RPM. I have thrown lots of chips, programers, intakes, and exhaust at 7.3 motors. What really matters is driving slower or get taller gears if you don't want to slow down. I just drove a 99 F350 4X4 AUTO CC LB DRW 4.10 up from Oregon to Alaska. 55 MPH average speed got around 17 mpg. My SRW 6 speed with 3.73 would get 20 mpg at 60 mph I lost about 1 mpg for every 5 mph increase. I had it Germany for a year 95 mph was fun but it sucked a lot of Diesel. Winter fuel will cost 1-2 mpg. I have to see how this new truck pulls my 5th wheel before I consider changing the gearing.
DENNY
 
#13 ·
You brought your Powerstroke over to Germany?

Interesting.

BTW, what were your RPMs in your two examples at 55 mph? And how much less economical is a DRW vs SRW if all other things are equal?

Thanks
 
#14 ·
I had retired and got a new job as arm candy for a Air Force 06. Good gig if you can get it! We shipped truck to Italy for two years then moved to Germany for one year. We even had a Ford Superduty rally in Germany. If I remember correctly it is around 200 RPM. I just sold the six speed I should have tracked it closer. DRW vs SRW with the same axle most reports I have seen say it is about 1mpg loss with the DRW given the same axle gearing. I think the gearing is costing around 2 mpg depending on speed. So you can figure extra cost will be whatever the extra fuel and maybe a few tires every now and then.
My F350 SRW was my daily driver/ 31 ft 5th wheel hauler. It did a great job but I put bigger springs on the 5 wheel and noticed it would sway me a bit more in heavy wind. I tend to drive like a old may when I tow because I am one. I figured I would give the DRW a try. I have not hooked up the the 5th wheel yet but empty it is a better ride than my SRW. I will see how it handles the 5 wheel stock and most likely upgrade with a mild tune. I think this is going to be a primary tow rig so most likely leave axle alone.
DENNY
 
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