Read through the whole 6.2 "Real World Mileage" thread. Mileages are all over the board........Appears as though most guys with 3.73 are getting 12 mixed and maybe 14-15 on the road, yes??

Replacing my 08 F250 6.4L Diesel (tuned, DPF/DOC delete) and would LIKE to get the 4.10 ratio as long as the fuel mileage isn't going to be a whole lot worse than the 3.73

Whaddya guys think? This is my daily driver, first and foremost, and I pull a 8500# loaded trailer a few times a year.

Thanks!

 

I just went through the same thing. For me I decided on the 4.30's as I tow heavy. (11k dry) Mileage wise some are getting better mileage in town with the 4.30's than the 3.73's. On the highway the 3.73's seem to be getting about 1 mpg better on average. Still they seem to be doing better on fuel than both the 5.4 and 6.8 did. I too am getting rid of my 6.4. I am done with diesels. I don't tow often enough to "need" one. I only tow about 1000 to 1500 miles a year and overall only put on 10K a year total as I catch a bus to work. My truck is for pleasure use only so because of not driving to work I don't burn allot of fuel. For you I would think the 3.73's will be fine if your max load is only 8500 lbs and it is only a few times a year. See what the others think.

 

I went with 4:30 hands down but unlike you this truck is not my daily driver.

 

I'm with Super08, would recommend the 3.73's unless you plan on going with larger tires later on down the road (which I will be). I was only getting 8mpg with my 2000 V10 w/ 37" tires so anything better than that was an upgrade for me. I won't be going bigger than a 35" tire this time around. Right now I'm getting around 10.5 in town, 13-14 or so on the highway.

The 5er I'm looking at has a 16k GVWR so I went with the 4.30's, will only be pulling it about 5-10 times a year but with the terrain out here in SW PA, I wanted the extra grunt. Diesel wasn't needed as I'm unloaded 80-90% of the times with short trips to and from work.

 

I'd like the extra off the line grunt from the 4.30, but how much worse is the gas mileage???

 

Only about 1 mpg hwy from what I have seen. Depends on the driver and terrain.

 

But the 4.30 seems to do better in town, huh? That works for me, most of my driving is mixed city/hwy....

 

Is the 4.3 ratio specification for the base models with 17" tires?
If so then the models with 18" tires will have a different ratio.

Looking at a tire spec web site I found the following:
LT245/75/R17E = 32" diameter
LT275/70R18E = 33.5" diameter

Using the formula

Effective gear ratio = Old Tire Diameter/New Tire Diameter X Gear Ratio

32 / 33.5 X 4.3 = 4.10

So a F250 with 4.3 rear and 18" tires has an effective Rear End Ratio of 4.10

Am I right on this????

So if I order a 4.3 I'm really getting a 4.10

 

Your logic is correct, but you are getting a 4.30. The rpm will be essentially the same as a truck with 265/70-17 tires and a 4.10 ratio differential.
I just worked it our on my spread sheet and there is only a 0.02 mph difference between the two at 1800 rpm.

 

Thanks, so if I go for the 3.73 than the effective ratio is around 3.5, correct?

 

With 18" tires yes. It depends with way you view it from. But yes If one had 3.55s and the other 3.73's the difference in speed at 1800 rpm is only 0.11 mph.

 

Thanks, Super great feedback, Sorry Jet if I Hijacked

 

I have always had 3.73 and seemed to work well for me.

 

I am thinking of trading off my 05 6.0L, after years of overpaying for fuel and maintenance costs, I think the gas engine would do me just fine. My biggest concern though is whether the 3.73 rear would be enough to tow my 5th wheel. According to the tow chart in Ford's brochure, a F250 2wd will handle a 12,500 lb. load with the 3.73. My rig weighs in at 11,200 lbs., I loaded it to the max for a 3 month trip and it weighed in it at 12,500 lbs. but that is not the norm. Not wanting to lose fuel mileage to the 4.30 rear is my other concern though I know it would pull my 5th wheel much better. I would like to hear from others that tow rigs with similar weights and see what they are using for rear ratio's and what fuel mileage they would be getting.

 

A follow up to my post: We travel to Florida about 2000 miles roundtrip once a year, and other than a couple of local camping trips a year the truck would be used as a daily driver. Thus my concern about fuel mileage driving around town with the 4.30 ratio. But if the 4.30 doesn't make that much difference in mpg, then I would assume this would be the better choice for hauling the fifth wheel. Comments anyone?