Okay guys, i know that 4.56's are a good bet for improving fuel economy as well as giving some seriously kick-*** improvement in acceleration but how much of an improvement in fuel economy can i expect? I'm not going to buy something for the sake of 1 mpg that will diminish once i install an intake and exhaust setup. I want an honest account of what they will do for me, i dont want to hear from speed demons about how kick-*** they are when it comes to acceleration, I can find this out when I pull up next to the first smart-*** in a Titan and kill him.
Can anyone give me a real account of how much of an mpg improvement i can expect?

 

MPG improvement = none with the 4.56's over your current gear. You will only lose MPG when increasing your gear ratio. It's pretty simple the more gear you add the more RPM you turn at a certain speed. The more RPM you turn equals more fuel which equals less MPG. If you were looking for more MPG you would want to install a 2.73 gear, that would get you more mileage. All though your truck would be a lot slower in the ET department.

Brad

 

It depends on what your driving. If you own a 3Rd Gen Ram then 4.56's WILL improve your fuel economy up to 65-70MPH. you can thank the 32" tall tires and the .67/75 overdrive for that fact.

I went from 3.55's to 4.56's and gained 3MPG at 65MPH.... This is a FACT and not an opinion.

DONT FEAR THE GEAR!!

And RPM’s alone do NOT dictate fuel consumption. Actually RPM’s have a smaller role in actual fuel economy than most think. It the load on the engine at ANY given RPM that determines your fuel economy... The 4.56's will only raise your RPM’s approximately 300RPMs @60MPH. The 300RPMs will lower the load on the engine and move the mechanical advantage to the rear end... With this less load on the engine you will see better fuel economy.

Actually you will see GREAT fuel economy from 0MPH all the way to 65-70MPH... I can get 20+MPG at 65MPH with my 4.56's. At 75-80MPH I can get approximately 16-17MPG so even at 80MPH its not so bad... and I have had it well past the 120MPH mark on the Speedo... all the way to "L1"... so top end is there as well.

SPEED SAFE, AIR RAM

 

BTW, i have an 03 Ram Hemi, i cant take not having money. I hate being broke all the damn time, I need money.

 

If this is true, why not go 4.88's or even bigger? When will you stop gaining mileage? If what you are saying is true, that by raising rpm you are decreasing the load on the engine, then does that mean if you run 1000 rpm more your load would decrease even further, there by giving you even more MPG???
I only ask these questions trying to understand how you gained MPG. You are the only person that has increased gear by that much and gained MPG, at least that I have ever heard of. If you recalibrated your speedo and haven't changed tire sizes or anything likr that..........I don't see how more gear = better MPG.

Please help me understand.

Brad

 

Air Ram, if you gained mpg it's probably not because of 4.56 gears. If you also increased tire size it brings rpm down and maybe you'll gain some. In general, with higher numerical gear, like 4.56, engine has to turn higher rpm to maintain same speed. Higher rpm usually means more fuel burned. I would admit though, that in some cases, especially with smaller engines, the gear change could bring engine to work in more efficient way and thus cause better mpg indirectly. But as a general rule, higher numerical ratio means lower mpg (think about comparing mpg in transmission with and without overdrive).

 

I'm Doing the gears to "re-gain" what is lost when i put 35" tires on my truck. I have to push the pedal that much harder to get to cruising speed and now it does not want to maintain cruising freeway speed, meaning O/D can't maintain the speed unless i'm doing 90 and even them i guess the weight of turning those tires is more than the O/D can handle. So yeah I will improve MPG to keep the tires size i have if i where running 37's(tires) or bigger I would probably go with the 4.88. If my truck was sitting on factory size tires i wouldn't even consider gears and if i couldn't handle the MPG i think i would be looking for a Civic.

 

Well there is a fine line... eventually raising your RPMs to a point will over come the benifit of decreasing the load... but we are talking a 300RPM (THREE HUNDRED RPMS) at 60MPH... thats NOTHING. As a matter in fact I had to remove my 20's and install a set of 17's that there 29.75" tall... so with the 29.75" tall tire and the 4.56's I got over 20.1 MPG on a2400 mile road trip from DFW to Deltona Floridy and back... this is to include ALL driving in traffic, around town/city and in between, not just highway. When I got home I averaged 456 miles a tank when all said and done...

Your not taking into consideration that you have a .67 overdrive. With this .67 overdrive your 3.55's become a 2.37 gear and your 3.92's become a 2.62 rear gear. Add the SUPER tall tires we have and that ratio gets even lower. On the FLIP side, the 4.56's become a 3.05 overall gear ratio... please tell me when a 3.05 gear became a BAD gear to have on the highway... Honestly its PERFECT for our combonation. And UNTILL you have experience with the 3rd Gen Ram and gears... your useing dated experience and your dated experience will cloud your judgement.

Again 30"+ tall tires, and a .67 overdrive are the reasons 4.56's are TAME on our 3rd Gen Rams. The stock ratios are literally to low and in overdrive they LUG the engine down... which consumes more fuel.

Also, on the third Gen Ram you do NOT need to recalabrate your SPEEDO after swaping gears... actualy there is NOTHING that needs to be done to the speedo after a gear swap. The speed sensor input is taking from your ring gear, so changing the ratio has ZERO effect on your MPH reading.


And no, Im not the only person who has swapped to 4.56's and GAINED MPG... your new around here and you have not been around long enough to follow the subject.


Im not speaking from opinion,again these are FACTS proven on the road in my 3rd Gen Ram!

 

I did not change the tire size... well I did throw on a set of "SHORTER" (29.75") tires for several thousand miles but I did NOT get any taller than 32" tall... and most factory tires are that hight. My shorter tires did not do bad at all either... the RPMs where higher but the tires where lighter... so It kinda equalled out.

Guys look up 4.56's in a search... you will learn that this is NO secret and that MANY people with the 3rd gen Ram have GAINED MPG with a 4.56 swap. My point is, if your trying to get better fuel economey DONT aim to lower your RPMs... Aim to lower the load on the engine at any given RPM... this is where the fuel savings will come from. Higher RPMs do NOT always mean more fuel.

 

Personaly I feel on the 3rd Gen Ram with the .67 overdrive and the average stock 32" tall tire the 4.56's are the perfect match. With a 35" tall tire I would go to a 4.88 without a second thought.

SPEED SAFE, AIR RAM