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Old 07-16-2013, 05:49 PM
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Re gearing!

12 inch bulletproof lift on the way! Running 40 inch M16s, has anyone re geared their trucks yet going with bigger tires? And what gears did y'all use? And if anyone is out there on 40s what kind of mpg are you seeing? Appreciate the help!
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Old 07-16-2013, 05:57 PM
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Most go with 4.56s or 4.88s when running 40s. I can't give you any mileage claims with that big of tires, but I doubt it'll be anything to brag about.
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Old 07-16-2013, 07:36 PM
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I don't see the need to go to 4.56 or 4.88 with the 6R tranny. 4.10 or maybe 4.30
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Old 07-16-2013, 08:08 PM
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Quote:
Originally Posted by WoodBoy View Post
I don't see the need to go to 4.56 or 4.88 with the 6R tranny. 4.10 or maybe 4.30


OP what gears you have now?
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Old 07-16-2013, 08:34 PM
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I have 40's on my 6.7 and also had em on my 6.4, the 6.4 deleted with 5" exhaust and spartan got about 17 highway and 14 city hand calculated. The 6.7 I have now has a h&s tuner with the factory exhaust and I get about 11 all the time. The question is what are you going to be doing with the truck after the lift. I don't tow heavy but I have 3.55's and it pulls like a freight train so I don't know if gears are really necessary unless you are going to be pulling super heavy. If I were you I would put the lift and tires on and see how it does without gears before pulling the trigger. Also going that big, if you plan on using the truck in 4x4 much at all you will need to fix the front driveline angles. I couldn't ever get the m16's to balance worth a crap on 24" wheels so I went with 20"s and toys on this truck and it rides alot better than the 6.4 did.
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Old 07-17-2013, 03:07 PM
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I appreciate the help! Most likely going with 4.30s for the gears if I do end up doing them. As far as towing nothing too heavy my Rzr on a lowboy.. Other than that a pavement queen that will see the beach a few times. Mainly wanting to change the gears for a little more mileage sake, I know the truck has plenty of power I have a mini maxx with the snyder hot tune and 5 inch exhaust
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Old 07-17-2013, 05:28 PM
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Changing the gears will drop your fuel economy. I have 40's on mine and get about 15mpg average, mostly consisting of city travel. I've towed my boat about 5,000lbs with the stock 3:55 gears and had no trouble. If your wanting the best fuel economy then gears is not what you want to do because it'll just raise the rpm's decreasing mpg.
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Old 07-17-2013, 06:38 PM
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Quote:
Originally Posted by brandonlee0034 View Post
Changing the gears will drop your fuel economy. I have 40's on mine and get about 15mpg average, mostly consisting of city travel. I've towed my boat about 5,000lbs with the stock 3:55 gears and had no trouble. If your wanting the best fuel economy then gears is not what you want to do because it'll just raise the rpm's decreasing mpg.
That is true to a point. Your truck has to work wayyyy harder then a say a truck with 4:30s to accelerate. So with all the extra work it has to do to accelerate it'll use more fuel. Also if you live in a hilly area regearing will increase your mileage because your truck won't use as much boost to maintain speed. And if what you say about lower rpm being better for mileage you should get better mileage than a truck with stock tires which I can say you don't lol. So to the OP I'd say go 4.30s and your truck and tranny will thank you. Also if you don't get any mileage out of it you will have a lot more power(but I'm pretty positive you will increase mileage)
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Old 07-17-2013, 06:54 PM
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I think 3.55's and 4.30's are both bad choices with a 40" tire. 3.73's with the 6R140 is plenty, and 4.10's would be overkill as the op has stated its a pavement queen.
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Old 07-17-2013, 07:06 PM
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Imo I don't think going from 3.55 to 3.73 would do enough to justify the cost. 4.30s are going to give you a large power boost, close to stock. I've noticed power loss with 35s so I couldn't imagine 40s, so if your gonna get crappy fuel mileage you might aswell have lots of power
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