I have a 03 F450 V10 6 speed, rollback tow truck that gets 5.9 to 7.7 MPG. With the 7.7 being straight highway, half loaded, half empty. 100 miles on a fill up (mid ship tank)is pathetic. I'm thinking of changing the 4.88's to a 3.42, or 3.73 gears. If I were to use the 3.42's, 5th gear would be at the same rpm's as 6th now. That would allow me to have the same criuse rpm's as the stock 4.88's for heavy loads, and run 30% less rpms when empty or lightly loaded. My truck weighs about 11,500 empty, and usually under 16,000 loaded (one car). Occasionally up to 20,000 gcwr, or my max will 6000 under Ford's GCWR. Has anyone with a F450 or F550 V10 changed to gears in this range? I'm thinking this might get me 10 MPG highway. LS

 

First, WELCOME to FTE!

I'm going to caution you, you WILL get a lot of attitude from people around here.

What RPMs are you running at 60-70MPH?

In many people's experiences here, LOWER gears are BETTER for MPGs with the V10 and heavy weights.

I fear if you went to 3.73's, you'd get WORSE mileage, AND the truck would no longer be able to handle all that weight. >11K lbs empty is pretty high. You'd need 4.88's just to move that thing around with any authority.

Going from 4.88's to 3.73's will drop your torque-to-the-ground by 30% - that's a HUGE DIFFERENCE! You WILL be sorry.

We have people here that have gone from 3.73's in their SD to 4.30's and gotten BETTER mileage when heavily loaded.

Plus, the fact that you might find it very hard to find 3.73 gears for that rear-end (Dana 135?).

 

I'd say you are definitely going the wrong direction. Just put in an aux fuel tank, and put on a fuel surcharge per mile on the tow bill. The other thing is train your right foot to keep the motor RPM's under 2000. The more under the better. I sure wouldn't change the gear ratio.

 

This truck is at 2400 rpm @ 65 MPH I usually drive about 70-75 on the highway, which is about 2600 rpm, too high I think. This truck has a Dana 80, so gears are not a problem. I think it would be more efficient at 2000 rpm, than 2400-2600. The gross combination weight rating is 26,000 and I will be under 16,000 98% of the time. My theory is for the 2% I'm loaded heavier, to drive in 5th instead of 6th, and the rpm will be the same as 6th gear with 4.88's. This truck will never get even close to what it's rated to pull. The other solution, is gears and a Cummin$$$$ swap. 6-7 mpg is too bad to deal with. This truck will pull staedilly from 800 rpm in 6th now, I would think 1800-2000 on the highway would not lug it at all. This area is very flat. LS

 

You might try checking into running a Gear Vendors overdrive unit. They are a pricey little item, but you'd have the overdrive gears you think you need to get the mileage out of that 10. There are some guys talking about it up in the super duty section.

 

Well if it's a 2WD truck you may try 4.10
If it's 4WD needless to say the cost of a gear swap doubles.
Might even snoop around for a diesel..?
Wish my truck had 4.88's, it may have soon!
If you find yourself needing someone to swap gears PM me, I'm just a bit south of the city.
Gene

 

Given 2600 RPMs, if you re-gear to 3.73's let say, you'll be at 1987 RPMs.

That's a HUGE difference. Sure, the torque curve is pretty flat for the V10, and it's putting out something like 85-95% of the peak torque at 2000 RPMs. But the torque-to-the-ground is 30% less.

And, as we all know here in V10 land, 2200-2300 on the highway is probably the MOST efficient RPMs for a V10.

 

If these V10's are most efficient at 2200-2300, maybe I should go 4.10's. My other tow trucks have been diesels for the last 10 years. They pretty much all got 10 MPG with 4.88-5.13 gears. My newest one gets 10 around town or 13 straight highway with the 4.30's (at 75-80 mph), and it weighs 11,500 empty too. I love to get 10 out of this truck on the highway empty. This truck is my backup unit, I saved about $7,000 over what a used diesel would've cost. Maybe I should just deal with the mileage, but sometimes I can't just leave things alone! If this V10 ever lets go, I'll probably do the Cummins swap. LS

 

I thought we were the only ones w/ a v10.I have a 99 F550 19" century steel bed 12360# empty,4.88 and automatic trans. We work the LA/San deigo metro areas.Right now I'm seeing 8 to 9.3 averaged out. This truck likes 65 mph and we allways leave w/ 2 cars from the dealership. These are mostly freeway miles,stop and go is a KILLER to all trucks,diesel and gas allike.for instance, we have 2 650's 260 cummins/allison auto w/3.90's 22' steel beds w/ stationary cabshields (16400# empty) this combo averages between 9.7 and 11.8 averaged city and highway. 2 cars to san diego nonstop at 70 (120 miles) i've got as high as 13.6 but, driving around town in traffic accelerating frequently as low as 8.I feel your pain , I bought a gas 550 for the same reason you did, the chassis cost 11500 used w/93K verses 15-18 for diesels w/100K+ miles. I also use the truck as a "backup truck" but it still gets used everyday.It boils down to a math problem and the money you save in the initial purchase you will probably spend sooner or later,the gas have proved much more reliable than the 6.0's some of my friends that work local areas are going gas next upfit.how much do you loose with a broken truck? Hard to tell customers your trucks down. Anyway, if your the only driver try driving in 5th for a day instead of 6th what do you have to loose? I had 2 7.5 gas 450's in the 90's that got 9 mpg (me driving)you got to get that much.Good luck!!

 

Mike, and LS, your information is much appreciated! Glad you're here!

 

Mike, I'd be happy with your MPG. mine averages about 6.8 overall. The 460's got better mileage with 410 gears and no overdrive. So much for technology! I love my 6.0 diesel. Hardly any problems. You can drive it as hard as you want with 400RWHP, and always get at least 10 mpg. The rear tires wear quicker though. Even when driving the V10 extra easy, the mileage is just as bad. I think I'll do a test on my next highway run and drive 55 the whole run, and see if it's any better. That will let me know if the gears will help. Lloyd

 

hey, if your deisel rigs are only geting 10 to 13 how can you think you can get 10+ with the v10 ?? in kc mo. today gas is 51 cents a gal. less than dsl. . get a bigger tank . ihave a f450 v10 auto that i tow about 20k in town get about 8-9 mpg . i have the 44 gal tank so the range is near 400 .i love the 4.88s see ya barry

 

LS, before you pony up the time and green to do a gear swap, make sure you have a clean air filter and a new fuel filter on her. Also give the maf sensor a spray of contact cleaner. These engines are picky when it comes to these things, and you can often cure a running problem with just a few bucks and a little time.

One other big strike that we have against us up here by the windy city is the winter blend fuels. Our Excursion has consistantly lost at least 1mpg every winter for the last 3 years we have owned her. Come summer, the mileage goes right back up.

 

I'd like to see 10 mpg straight highway, even at 65 mph, where my diesel will get 13 straight highway at 75-80 mph(4.30 gears). I'd settle for any improvement though. LS

 

IT does have a new air filter, and fuel filter. Also has fresh Mobile one synthetic. I'll try cleaning the MAF. I've had this V10 since summer, and mileage never changed, it's always been bad. I had one of my shops hook it up on the computer, no problems found. LS