I currently have a '96 7.3 and am considering an upgrade to the '08. I really want the towing power of taller gears. Does anybody have an idea how much difference in mpg I would see between a 3.73, 4.10 and 4.30. I realize the 6.4 with anything will be a tremendous increase in towing power over what I now have but I hope/expect this next truck will last a long time and I want to be sure what rear I want. Thanks.

 

It's going to depend on how much weight you're pulling, if it's not too much, and not very often, the 3.73's will net the best mpg overall.

 

I had a '99 F350 drw 4wd crewcab with the 7.3 and a 3.73 gear. The truck was modified with Banks turbo and exhaust mods. Normal driving around town without a trailer with a mix of stop and go city traffic, and some open county roads, normally resulted in 14 to 16 mpg. Highway driving with a 12,000 lb trailer with the cruise typically set at 78 resulted in about 9.5 mpg.

I have an '08 F350 drw 4wd crewcab with the 6.4 and a 4.30 gear. It has 850 miles. The same normal driving without a trailer has resulted so far in 12.3 mpg. I just drove 400 miles yesterday on I-75 varying speeds between 65 and 80 with most of the time spent in the 70 to 76 range. The truck got 10.3 mpg with no trailer.

I got the new truck to tow and will have a new hitch on next week and report on the first trailer pull sometime thereafter. I expect it to be an awesome towing machine as the power output appears to be strong and smooth. I am curious what fuel consumption will be with a trailer and hope it is not much worse.

One big difference between the two trucks, aside from the gear ratio, is the boost of the turbos. My stock 7.3 had a max boost of 12. The max boost after Banks mods was 26. The new truck was pulling 32-34 pounds boost yesterday going up a modest hill in Florida with the cruise set at 75mph. The power appears limitness but there apparently is a lot of fuel pouring into the motor.

Bottom line so far: if you need the grunt of a 4.30 be prepared for substantially worse fuel consumption with the 6.4.

Incidentally, it would be helpful when folks post their fuel results to state the type of truck as a F250 shortbed cab srw with no 4wd is obviously going to get a lot better mileage.

 

Any truck I get will be DRW, long bed, crew cab, 4x4. It will be used almost exclusively for towing and I know it will not get good fuel mileage. Just wanting to know what the difference might be between the three rears-all other things the same. Would 1 1/2-2mpg diference be about right between the 3.73 and 4.10? And about the same between a 4.10 and a 4.3? This is too much money to spend and not know I made the right choice. Thanks again.

 

I would get the best gearing for the load your going to haul/tow and let the fuel mileage chips fall where they may. If you get 3.73 gearing and you can't keep it in high gear or have to downshift for every little hill because of what you are towing you have not gained squat over the 4.10s or 4.30s.

 

I wish someone, preferably with the 4:88 gears would try the gearmore overdrive unit. It seems to me that it would be the perfect combination. Power when you need it and fuel economy when you don't.

 

I have the 488's and that unit sounds real interesting, but I'm petrified of anything aftermarket voiding the warranty. So far my truck empty, no towing, in town, is getting 9.2 avg, and I'm keeping my foot out of the turbo as much as traffic will allow.

 

you have the 4.88's but what are they in?

 

I'm pretty sure he has an F-450.

 

yep 08 f450

 

I discussed this with my Ford Dealer. He said it would have to have caused a failure before they would not honor the warranty. If it takes more time to remove the item then they would charge extra to remove and replace.

 

The problem with the overdrive unit is the costs associated with installation that you don't think about when it first comes up. You have to pay for the unit, pay for installation, pay to get the rear drive shaft shortened and if you have a 4x4 you have to buy a new custom front drive shaft because the stock one will be too short. This adds up in a hurry. $$$$$$$$

The best solution in my opinion is to buy a truck with a high rearend gear for example 4.30 in the 450, 410 in the 350 and 373 in the 250 and get a six speed with the granny gear. If you don't have the power to pull in OD, drop it down to 5th. Still better mileage than no OD in an auto.

 

Are the srw trucks coming with options for 4.10's? I was thinking about getting the 4.10's so that I could run 37" tires and be close to stock....or maybe a stock truck with 35" tires on it.

Currently I have an 04 with 35" tires and the stock 3.73 gears. I probably average 12 to 14 mpg.....mostly interstate driving. I use to have a 2000 gasser. I got the 4.10 gears in it and ran the 35" tires. While compared to my 04, mileage and power was a lot less with the gasser, it did appear that the two were equal to those with 3.73 gears and stock tires (which I think are about equivalent to 33").

But I keep seeing all these trucks running around with 6" of lift and 37" tires on 18 or 20" rims. While I know many people are running the 37's with the 3.73 gears, I don't think I would be happy with that. So, I was thinking that if I got a new 08, I would aim for the 4.10 gears to help out with the 37" tires.

 

Very nice!

Bottom line is if you need the towing power of the 4.88's you are going to get worse gas mileage. I looked into the gear venders unit for my 06 F250, it was way to expensive to justify for increased gas mileage. Best case it would take +/-125,000 miles to pay for itself.
Lets say fuel is $2.50 a gal and you are getting 10mpg without the GV, fuel cost is $0.25 per mile, with GV you MAY get 12 mpg fuel cost is now $0.208 per mile. Cost of GV installed with required mods +/-$6,000. Difference in cost of fuel is $0.042. Using these figures which are pretty generous in terms of fuel cost, MPG increase and GV cost it would take 142,857 miles to pay for the GV. The real purpose of the GV is not in MPG but in more gears in your power range to help pull big loads.