I've got the 3.55's and am yet to decide how well I like them. They are pretty decent on highway but when I compare it to my Tundra, the 390ish hp doesn't feel quite that potent because 1st is such a long gear. I think mine does 50mph in first gear. I think 80 mph is about 1800 rpm though so that's great for highway.
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I also have no issue getting 15ish in the city if I drive it right, all about MDS kicking in and staying on as long as possible. My secret is using cruise control even in 35 zones. Of course traffic dictates that, it is not bad where I live.
As for gear ratios, it is the final ratio that really matters, especially when you want MDS running as long as possible.
I am a believer that if you have the 20s the 3.92s are right for this truck and the 17s 3.55s are fine.
Why do I say final ratio? If you have 3.92s in a truck with stock 20s on it and you decide to "rice it out" and put on 17s with next to no rubber (ie small diameter tire vs the stock 33" tire) your MPG will go down even though you did not touch that gear ratio. With that setup your final ratio will have changed quite a bit.
You will see people who go big on tires will put 4.10, 4.56, ect, this is due to the massive rotational mass of the tires, the taller gears help to offset that and keep the acceleration "seat of the pants" feel, again, final ratio.
The 3.55 is a decent gear. I have no idea how it would perform in a 4x4 since it doesn't have LSD. I'm not sure what kind of off-roading you're looking at doing, but if it's anything other than going down fire trails, then I'd go with the 3.92. I've driven both the 3.92 in a test truck I had for a number of days, and then the 3.55 in the one I bought. With the 3.55 the kick in the pants just really isn't there. With 390hp it's got some get up and go, but you really feel like the truck is the full size truck that it is. The 3.92 really makes it feel sporty when you give it a little gas.
I'm eventually going to put 4.10 in mine. All I need to do is save up the cash first. Of course to do that I need to stop all these things that keep coming up that keep sucking the bank account dry.
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2009 4x2 Brilliant Silver Crew Cab Sport Mods: Dodge Nerf Bars, 20% tint, iPhone Cable, Mufflex 14, Line X, TRX Grille, Debadged, R/T Grille Badge, Weathertech Digifit, Leer 700 Tonneau Next Mod: Airaid Cold Air Intake (January)
Tell me your secret. I hardly go above 2000 rpm and cannot get more than 13.
Do you use premium?
Is that by EVIC or by hand?
By hand (Evic reads higher I think, although I do not check it regularly). I do not use premium, but I do run 100% gas (there are a few stations around here that use no ethanol, and that could be helping a little).
By hand (Evic reads higher I think, although I do not check it regularly). I do not use premium, but I do run 100% gas (there are a few stations around here that use no ethanol, and that could be helping a little).
Aren't you suppose to run a higher octane. In my county there are NO 100% pure gasoline stations.
I have the 3.92 rear end and am very pleased with it. I am getting around 22 mpg (imperial gallon) on the highway and 17.5 (imp.gal.) in town driving. My last 2 trucks were F-150's and they never saw more than 20.5 / 16.5. My dodge isn't nearly broken in yet so I am very happy and I would reccommend the 3.92.
I consistantly get 12 in city driving. Haven't gone on too many highway trips but it's been getting 20 with the cruise set on 70. This is with the 3.55 ratio and hand calculating on every fill up.
Hey do you wish you had at least 392's or even 456"s, I hate the sluggish pull, makes ya wonder if it is really 390 hp
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09 Sport Ram, Hemi 4x4...no power adds, pace edwards power locking tailgate, updated from to REN My Gig and added the uconnect module....required Star scan at the dealer//bad experience 14 hours 2 dealers.
