Hey everyone, new to the forum and new to the 2500. Bought a 2005 2500 ram 4x4, 2 inch level, 35 inch tires. It has 3.73 gears from the factory. Should I go with 4.56 gears? Will I gain fuel economy? I do highway driving to work and back then all city after that. What is gonig to be the overall cost?

Also, what exactly changes when doing gears. Is it front and back?

 

It's been covered frontways, backways, right side up, upside down and sideways. Might I suggest the search function:

 

You will NOT gain fuel economy. It'll have better pick up at lower speeds and if you don't change the ring and pinion in both the front and rear diff's your 4wd will not work.

Oh yeah, and plan on spending ALOT of money.

 

you absolutely WILL pick up fuel economy.. in stop and go traffic anyway.. it WILL hurt your highway mileage though, but not so bad with the trans your running.

without rehashing a subject that has been sliced, diced, and sprinkled with all kinds of opinions, the basics are this:

heavy trucks benefit from leverage of low gears, to get them rolling.. the same leverage hurts top end.. if you spend an appreciable amount of time on the highway and at speeds north of 70mph, you're going to see economy drops.. If you spend majority of your time in stop and go, and/or at speeds less than 60, you will see an increase in economy..

the feds put the squeeze on auto makers to produce fuel efficient vehicles- they have to maintain an average across all makes and models.. they pay when they don't.. the means to determine mileage is mathematical... engine displacement, and overall gear ratio (which determines RPM's at certain speeds; and is a fixed thing) are the major factors for determining a vehicles economy rating.. Manufacturers cheat by producing vehicles with higher (lower numerically) gears.. it gives the appearance that they get better mileage than they do..

RPM's through a particular ratio is a mathematical thing- and can't be argued.. BUT.. LOAD can.. are you dumping excess fuel to achieve or maintain a certain speed? If your engine is 'building' speed, you are.. if you have found a nice place to 'plane' the engine- you aren't.. A good example is a generator.. once the power load has been established, a gas powered generator finds a suitable RPM, and trims the engine's fuel to support that RPM.. In a vehicle, it's almost impossible.. you encounter winds, hills, traffic, ect.. A lower gear (higher numerically) will allow you to achieve power to the terra to sustain a speed easier than a higher gear..

if you haul or tow, or run heavier, taller tires- low gears will save you hugely on fuel.. if you use your truck like a car, lower gears aren't going to help you as much- but it will still help, because your truck isn't a car, and the curb weight is substantially more..

 

Yep, what Drew said...

Re-gearing should be done to make up for lost power when adding larger tires, for better performance towing/hauling, etc. YES, you should see a modest MPG improvement in the above situations, especially when driving "around town", but in all probability you'll give it back when cruising on the interstate.

Re-gearing should NEVER be done solely for a means of gaining fuel economy, even if you drive 100% of the time in the city, because it'll take you the life of the truck (or longer) to make up for what gearing costs you (unless of course you can set a ring & pinion in an AAM axle yourself - few of us can).

That said, I think the biggest "waste" is the factory putting 3.21 in half ton (hello, 4th Gen owners) or even 3.55s with 20" tires. I guess 3.55s are ok with lighter 17s at stock (32" or smaller) tires IF you don't tow/haul AND the majority of the time spent driving is on the highway. Likewise, I think 3.73s is a waste on a 3/4 ton truck, I mean you're buying the 3/4 ton as a tow/hauler or you would buy a half ton. I mean c'mon, my 3800 lb. Jeep has 3.73s, how could this be a good gearing in a heavy truck? The only exception I see to this would be a CTD because a diesel has the low end torque to compensate for gearing, it makes 90% of it's power way down low in the rpm band. IMHO a 3/4 ton gasser should come STOCK with the optional 4.10 gearing, especially a Hemi which makes so much of it's power up in the mid to upper rpms.

Matt, you want your Hemi to feel like a Hemi with your 35" tires then re-gear to 4.56s and trust me, your transmission will thank you for it too, BUT don't do so as a means at getting better fuel economy off of a 3/4 ton truck - ain't gonna happen - that's why they make Prius'...

 

In some instances moving up to a 2500 gasser is more of a lateral move from a 1500 then a vertical move. You can look at a 2500 as just a tow/haul vehicle, but if you were to compare a ½ ton to a ¾ ton in terms of gaining for example; height and gearing at the cost of maybe a couple of mpg. The ¾ ton trucks also have a much more aggressive stance then the ½ tons.

When I brought my ¾ ton truck I had these things in mind: I gain height without need of a lift kit, a solid front axle instead of independent suspension. Also, in my case I got the truck for thousands under Street Value and my old 5.2L only got one more mpg then my Hemi does. In terms of towing I have no complaints either, I’ve a pulled a 8500lbs. trailer a couple of times and the truck performs as it should.

 

I have been looking into this for a while also. My concern is that I will be doing most of my driving on the city and dont do over 70mph much. But my drive to school is 4 hours and I am usually 65-70 mph and I take a 6 hour trip 1 or 2 times a year to gramps house at 65-70mph. I assume my mpg will be down which is fine but will this put extra strain on the tranny or anything else? I have an 04 2500 also and plan on upgrading my 3.73 I am just not sure what yet. Still waiting for my 35's and my lift kit.
I am still learning about gears now so just trying to get more info as well with you bud

 

I agree with this. 3.73 is a poor gear ratio IMOvfor those of us that actually use our 2500's as a workhorse
I currently own two trucks (see sig) and tow a 14' enclosed trailer almost every day for my business. The 08' has 3.73's and 285 tires while the 93' has 3.92's and 33" tires. The 3.73's are pretty pathetic considering the size/class of truck they are in, and they were less than satisfactory when the truck had the stock 265's. My 04' hemi 1500 i traded in for the 3/4 ton had 3.55's and that combo IMO worked better than the 2500 and 3.73's. 3.73's in a heavy 2500 with a motor that has a sky high power band, come on dodge. Granted the hemi can still show the 5.9 magnum the tailgate pretty easily unloaded, I do prefer to tow with the 93' and the 3.92's. I know there is a significant difference in weight between the two trucks, but there is also a significant difference in power and torque between the two motors. The mechanical advantage of the gearing is beneficial if you plan on towing often or you do alot of drive <70mph.

My 08' will eventually be getting 4.56's since I bought I to tow. Until then the 93' will just have to wait on its retirement.

 

Going to numerically higher gearing will actually ease the wear and tear on your transmission. Reason being that your RPMs will be higher at a given speed and remain higher, thus your transmission doesn't have to search for the proper gearing when towing or traveling hilly terrain.