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Discussion Starter #1
I have 37-12.5-16.5 on my 00 7.3 .tires on and everything seems to run good but towing with 3.73 gears is not always great.

I searched and didnt find many guys talking about their mpg with 37s and different gear ratios so i was wondering what yall get with 4.10s,4.30s, or 4.56.

Also can tunes help my bigger tires? Can anyone tune for shift points because of the tire and gear ratio? do any of yall run propane injection for mpg increase? i know you will be paying for propane also but something ive been looking into. thanks

I get around 10 city and 15-17 highway..
 

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Discussion Starter #2
anyone? please and thanks just trying to see if i want to gear up my truck or not
 

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Well, seeing as how those tires are going to effectively make your gear ratio something like a 3.12, I know gearing down your axle will help towing and driveability. However, your gearing is likely close to optimal for MPG, maybe a little tall. if you really want to have your cake and eat it too, gear down to like 4.30's and then get a gear vendors overdrive. that way you could tow, and you'd likely get close to 20mpg on the highway.
with those tires, however, don't expect much more in town. that's alot of rotational inertia to overcome.
 

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Discussion Starter #4
yeah i figured that in town i wont see anything much better than that and thats fine with me. Im just trying to get the best bang for my buck right now with the way fuel prices are. I know i should probably just ditch the lift and tires for best MPG but i like the way it looks and its a hell of a lot of work to trade the lift or sell it to buy a stock lift. I guess i will look into seeing what i can do for gears and gear vendors overdrive. Thanks for the advice and help bud
 

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No problem.
How long is your commute? have you tried just driving like a granny? might not need to spend that kind of dough.
it also may be more intelligent to buy a beater or bike than change the truck. my bike gets me 42-44 mpg and is a blast to ride... if only it would stop raining.
 

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Discussion Starter #6
well I play college football in kansas and the commute during the week is slim but during the weekends i go home to MO and work about 30 miles away one way and sometimes tow a 14,000 pound excavator and a 10,000 pound loader so thats the main reason for gearing. I wouldnt mind having a bike but like throwing my extra $ into this damn money pit of a truck more lol.
 

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Discussion Starter #7
need to delete this dang ebpv first though. I can see the black smoke pouring out when its warming up while driving around in the morning. Can i just take the clip off that valve and somehow tie up the lever for the plate ebpv
 

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Im in the same postion you are man, i need gears but never could find out what gear i needed on the forums. i work for a well know 4wheel center and they all recommend i run 4:56's with my 37's. I wish i had done put the gears in to answer your question better but it wont be long before i order the yukons. hope this helps
 

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Black smoke when warming up? that doesn't sound right to me...
 

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Discussion Starter #10
not sitting there. when you are driving and the truck hasnt gotten to running temp. When the ebpv kicks off while im giving it gas it blows black smoke .

So has anyone just ran 430s without gearvendors overdrive? with a lift ?
 

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My truck has 37s 4.30s and 6" lift. Its decent. but I would go with 4.56s if I were to choose again. it makes about 2100rpm at 65-70mph on the highway as is right now with the 5r110. its not bad though.
 

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Discussion Starter #12
whats your mpg like? if you remember before and after at all? im guessing you went from 3.73 to 4.30s corrrect?
 

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Ive got a 6" lift and 37x13.50 MT tires. I get about what squeak12 says he's getting. I have worn out injectors and hpop too. I drive like grandpa Jones until I get up to about 40-45 then I accelerate more normally.

I think I could eek out another mpg or two by dropping down to a 35" tire.

The op is running an 8" lift if that makes a difference.
 

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With you towing 10,000-14,000lbs I would most likely go with 4.56s. Great for towing and around town but will push a little more RPMs on the highway.


I ran 4.56s with 38s for years. 12-13mpg around town and 15-ish on the highway.
I stepped down to 325/60R20s earlier this week, but barely have driven it to see my MPG now.
 

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For 37's I would go NO bigger then 4.30 gears.

I really get a kick out of guys driving around in a 8k truck, lifted on 35-39" tires asking how to improve there MPG...

Its a brick, a heavy ass brick.

Drive it, fill it when it needs it.
 

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@csipsd-You're right about peoples expectations being a litle 'off'.

But if he could run a 35 vs a 38 and save 2mpg's it'd be worth it right? I think he's just looking for optimal gearing for his truck. He said he's got an 8" lift in the first post so I dont think its going to improve much. Thats a lot of lift on a sd. My 6" is plenty big.

Im thinking about running a 35x12.5 or 13.5 on some 18's when Im ready for new tires.
 

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Discussion Starter #18
lol yeah im not looking for just mpgs out of this whole situation of gearing the truck back up. I dont tow every day or even every week. More in the summer with the camper and at the job.

But all i was wanting to get out of this was.. If i gear this thing up to 4.30s from 3.73s will i see a big drop in mpg? because i could live with not having as much power when towing if i was going to lose a ton of in fuel saving when i wasnt towing anything.

From what i understand I dont feel like its going to affect it much because the guys running 4.30s are getting the same mpg as me right now and have enough power to pull. So it would be a win win right? or do i have something messed up in this equation?

By the way guys thanks for the help and opinions
 

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Yes, Mine was about 13ish in the city. with the original 35s and 3.73s. and about the same now with 37s and 4.30s. you'd loose mpg by staying with 3.73s IMO. you'll use more fuel because the engine is being pulled out the powerband.
 

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Discussion Starter #20
See thats the way i understood it but thought maybe turning more rpms with the larger tires might make it want to use more fuel.. I dont know really about 13-16 is best ill see either way.

Looking into buying some pretty seriously.
 
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