Gear upgrade?
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Joined: Jun 2013
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From: SW Washington
Gear upgrade?
I've an '03 F250 6.8 4wd Supercab with an 8' bed and 3:73 gears. I pull a 13k 5r over many 5% and better grades, about 6k miles per year. I use it mostly for towing during the summer months in the western states. Here's the story: When I am pulling steep grades it feels very underpowered. I often have to downshift to either 2nd or 1st. 2nd gear over a 5% grade at about 40MPH or 1st gear on 6% grades at 30MPH. I really don't mind keeping it at about 3k rpms but I would very much like to be able to make those grades with less stress. The truck has a y-pipe conversion, rebuilt trans with heavy duty billet converter, shift kit, 5 Star Tuner and a 6.0 trans cooler. Zero problems with overheating. I am running 275/65 R18 tires (31.5"). I haven't seen much of a change in mileage or power by using premium fuel - enough to justify the increase in cost. Here's the question: will changing to 4:56 or 4:88 gears make a substantial change in power when pulling steep grades? Some grades are up to 14% (no kidding- Grand Staircase Escalante in Utah). The truck pulls just fine on the flat up to about 4%. I rarely use OD and never above 3%. I don't mind spending the coin for an upgrade but want to feel like it's the right move. I get an average of 8.5 MPG when towing over the summer; not too bad considering the load. Do you think the fuel economy will increase a bit by regearing? I love my truck! Uses no oil at all between changes and never overheats. Thx in advance for your responses. I have read similar posts but haven't seen any responses about the change in power for the kind of load that I am pulling over similar grades.
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From: ALPHA ,NJ
If you're going to stay stock size 31-33" and only tow I would recommend 4.30s. Going to a 4.56 or 4.88 might leave your unloaded driving on the highway a bit to be desired. I have 35s and I will probably be doing 4.88s next year some time.
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From: Breckenridge, TX
You're feeling underpowered because you're at the bottom red X, and you need to get to the higher blue X or you're leaving half your power unused:
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From: Media PA
Thanks for the tag Stewart! 
Donordad, I tow an 11,300+lb TT all over the East with our 2V V-10 EX, our hills are just as steep in places just not as long typically. My EX started out with the same 3.73 gears you have now and it too felt underpowered while towing the then 9,500lb TH. I swapped up to 4.88 gears which completely transformed the EX into a much, much better tow rig. With the same 32" tire's the towing mileage improved from 6.5/7 up to 9 MPG with same load over the same route at the same speeds. The unloaded mileage did drop from 14-ish to 12.5 on the highway, but the big wagon is a dedicated tow rig, so I was OK with that trade off.
After the gear swap I went to 35" tire's, Banks headers and 5 Stat tunes. With the taller tires it's now at an effective 4.30 ratio, still tows great (even with the bigger heavier TT now) and sees 8/9.5 MPG towing and 14 MPG running unloaded at 65 MPH. I do tow in OD and it can hold OD at highway speeds for most Interstate Highway grades here in the East, and when it does need to downshift on the bigger hills it pulls hard enough in 3rd ar 3000/3200 RPMs to accelerate back up to speed.
If the truck in question is strictly a tow rig with little unloaded use I would maybe consider 4.56 gears to counter the slightly higher weight and fiver profile as well as the longer steep hills and higher elevations. If it does see a good deal of unloaded use then 4.30s may be the better combined use choice which will still provide a nice towing performance increase.
Donordad, I tow an 11,300+lb TT all over the East with our 2V V-10 EX, our hills are just as steep in places just not as long typically. My EX started out with the same 3.73 gears you have now and it too felt underpowered while towing the then 9,500lb TH. I swapped up to 4.88 gears which completely transformed the EX into a much, much better tow rig. With the same 32" tire's the towing mileage improved from 6.5/7 up to 9 MPG with same load over the same route at the same speeds. The unloaded mileage did drop from 14-ish to 12.5 on the highway, but the big wagon is a dedicated tow rig, so I was OK with that trade off.
After the gear swap I went to 35" tire's, Banks headers and 5 Stat tunes. With the taller tires it's now at an effective 4.30 ratio, still tows great (even with the bigger heavier TT now) and sees 8/9.5 MPG towing and 14 MPG running unloaded at 65 MPH. I do tow in OD and it can hold OD at highway speeds for most Interstate Highway grades here in the East, and when it does need to downshift on the bigger hills it pulls hard enough in 3rd ar 3000/3200 RPMs to accelerate back up to speed.
If the truck in question is strictly a tow rig with little unloaded use I would maybe consider 4.56 gears to counter the slightly higher weight and fiver profile as well as the longer steep hills and higher elevations. If it does see a good deal of unloaded use then 4.30s may be the better combined use choice which will still provide a nice towing performance increase.
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