I have a 05 2wd 4.6L with a 3" lift and 33/12.5/17s. Sice putting them on the truck has been pretty sluggish and gas mileage dropped. My question is what gear ratio should I put in? I can't decide between 4.10s or 4.30s. What would be the best for 50/50 hwy/cty driving? To me getting my lowend back is more important than gas mileage but I don't want to lose even more gas mileage from the gear swap. Thanks in advance guys.

 

I say 4.30s only because if you ever decide to get larger tires, I really don't think your going to lose much gas mileage going from 4.10s to 4.30s.

 

I was thinking the same thing. I should gain some mpg back in the city right? I know lowend will be much better. Thanks for the quick reply man.

 

I would say 4.10's. I would say you will loose alot more in highway mpgs with the 4.30's than you will gain in city driving. but I do agree if you think you might someday get bigger tires like 35's it would be better to get the 4.30's. tough call I have debated the same question but I have a 4wd so 4.30 is not an option so 4.10's will be the choice for me. if I find someone that makes the 4.30's for the front I will go that way as I think I might get 35's someday. but I am 90 percent sure you will loose more in highway mpgs than you will gain in city driveing if you stick with the 33's especially if you go speeds greater than 65 on the highway. if you can keep it under 65 it might not be so bad. it will definitely help your take off the line. if you get the 4.30's keep us posted on the results. I am quite interested in the results.

 

Yeah thats why I'm torn between the 2. When I'm on the hwy I definately drive above 65. Decisions, decisions...lol I'll keep ya posted.

 

Think about it this way. Gear charts say 4.10s will bring your truck back into the stock gearing with 33s which would get you about the same gas mileage as stock right? Well than it would only be a little worse than STOCK with the 4.30s and probally still better than what your getting right now on the highway.

 

I have seen the gear charts and 4.10 brings you back to stock with 35's not 33's.

 

I don't know. The gear chart I looked at said the best all around performance/gas mileage was 4.10s with 33s, 4.56s with 35s, and 4.88s with 37s, and so on. Im not an expert on gearing but thats just what I stumbled upon.

 

Ide say Atleast 4.56's

I have 4.11's on my truck with 29" tall tires. 4.30's would better suit me.

Don't fear the gear.

 

Can anybody give me a link to one of these gear charts? Thanks

 

ok I was second guessing myself so I did a little searching and I did find those charts that thumpermx113 probably seen. but those charts do state they are based on a manual transmission and a automatic transmission will have higher rpms due to transmission slippage. I still cant find the chart I seen a while back that I was baceing my response on. I did find one chart that calculates your rpms for a automatic transmission you can use it to help you deside just read the rpms for your tire size and and gear ratio and speed traveling. I put in my tire sizes and speed I travel at on the highway and it was pretty acurate. hers a link

https://www.f150online.com/forums/link.cfm?link=http://www.ringpinion.com/content/calculators/RPM.asp

ok with that calculator you should try to pic a ratio that keeps your rpms below 3000 rpms with 2500 to 2700 beeing best for optomum gas milage. and 2700 to 3000 being a good daily driver rpm meaning it should be good for city driveing too. it has been my experience that as soon as your rpms hit and go over that 3000 mark your gas milage goes down. I did a trip a while back where I did 75 mph to 80 mph most of the way. my gas milage was like 1.5 to 2 mpg lower than if I gad done that same trip at 10 mph slower. thats just my experience.

I also came upon a simple formula you can use to help you. it is as fallows:

(new tire size) / (old tire size) X (old gear ratio) = (new gear ratio)

this formula makes sense to me and tells me if your old tire size was 31 and your new tire size is 33 and you want to return to a stock 3.73 ratio (which I think is optomum daily driver ratio for stock tire) you would need a 3.97 gear ratio this tells me anything higher than 4.10 might be too much gear for any kind of reasonable highway milage. if you plug 35's into that formula you come up with 4.21 gears to return you to the 3.73 ratio. which tells me the best ratio for 35's would be the 3.30 ratio available. I think you will loos arround 1.5 mpg on the highway and maybe gain .5 mpg in the city if you choose 4.3 over 4.10 but you will also get better performance off the line with the 4.3's so if better performance is more important to you than the 1 mpg you might loose on the highway I would say the 4.3 is the choice.

 

sorry that link didn't seem to work try this.

www.ringpinion.com/content/calculators/RPM.asp

 

Thanks for the help Jason. Sounds like 4.10s are the way to go. I dont think the performance increase with the 4.30s would be worth the mpg lost. Thanks again man.

 

Just for the record. I didnt lose MPG on the highway with my 4.11's with 29" tires, I gained.

 

What's your avg speed on the hwy?