Gear Ratio discussion

RescueF250 · Jul 10, 2012

What gears are you running ? With Tire sizes. What gains do you see ? Rpm range. ?

Currently I run 4.30s with 38's. Thinking of dropping down to 35's should I keep the 4.30's in it or go back to 3.73 ?

RedSmokey · Jul 10, 2012

Im not sure how much a difference it makes that I'm in a 7.3 but I still have the stock 3.73's with my 38.5" tires. Thinking of going bigger in which case I will be changing the gears. Wonder what would be good with 42"-44" tires

91turbogsx · Jul 10, 2012

I have 35s on mine with 3.73 gears. I can cruise at 60 (almost all speed limits here are 55) at about 17 or 1800 rpm. And as far as mileage I try not to pay attention to that. LOL

colo_dually · Jul 10, 2012

Are you looking for information on lifted trucks only, or stock hieght as well.

I run 4.30's with stock DRW 245/75R17s, at 60 mph I see 2,000 on the tach.
Mileage 14.5 mpg with stock tuning, and manage around 15.8 mpg with aftermarket (had some tanks end up better).

Betarocker · Jul 10, 2012

4.10 with 37s, ZF6 trans. Way better than 3.73 with 35s I had before. EGTs down, economy improved.

RescueF250 · Jul 11, 2012

So I'm gonna say 4.30's and 35's probably wouldn't be to hate full, she'll just pull like a bat out of hell then.

Dave · Jul 11, 2012

4.30s and 35's would put you at roughly 2300rpm at 65 mph.

It wouldnt take long to get to 65mph but your engine will be screaming at 70mph unloaded.

Id go with 3.73's and 35s with your setup..

Layson · Jul 11, 2012

RedSmokey said:
Im not sure how much a difference it makes that I'm in a 7.3 but I still have the stock 3.73's with my 38.5" tires. Thinking of going bigger in which case I will be changing the gears. Wonder what would be good with 42"-44" tires

I would probably roll with 4.56's or 4.88's...

I have 4.30's with 38's right now. Great combo.

Dave · Jul 11, 2012

4.30s with a 42 would be perfect

sirnunya · Jul 11, 2012

I had 4.30's with 38's and with 40's. Liked it a lot better with 40's. Mine was an auto 7.3l.
Also had 4.56's and 38's on same truck and did not like it at all on highway.

35's and 4.30's would suck if you do any sort of highway driving above 65mph. I think 4.10s and 35's would be pushing it as well, unless you tow heavy a lot

For 35s I would do 3.73

For 42-44s I would do 4.56-4.88

chappy · Jul 11, 2012

I gotta say I'm not real happy with 35's and 3.73's. I would like to try 4.30's and see what its like but thats some coin for me to not like. My milage is around 14-15mpg . I'm gonna be curious how you like it. According to the calculators it is just a little higher then stock and 3.73. I think it calls for 4.20's to match the factory setup.

stuckinmud · Jul 11, 2012

I have 4.30's on 35's. When I had the 6.0l it would turn about 2150 @ 70 mph with a corrected spedo. Now with the dodge trans and 2 less cylinders its slightly different lol.

When I did the math I figured it was close to running the oem tires at about a 3.90 ratio. This was in the middle of the factory 3.73 and the 4.10 option. Keep in mind in 05 4.30 became the tow boss option but the tire size became slightly taller so it is sort of the equiv to a 4.10 gear on a 99-04 truck w/ stock tires.

It is easier to get it moving when towing/ racing and really not all that bad on the highway.

tbsimmons · Jul 12, 2012

In my 04 I had 35's wit 4.56's. I liked them, but then again I am not the guy driving 85 in a lifted truck.
I got them mainly for towing the trailer.
The 6.4 has 4.88's. Both I like towing not unloaded, they suck.
If you dont tow, If I was going to swap gears, I would get 4.30's with 35-38 range, then 4.56's above that. I think 4.88's are a little much.
If you do tow, I would want the power range in the MPH you usually pull in. It helps the drive train out a lot.

RescueF250 · Jul 12, 2012

Im fighting the decision about lowering the truck down to 35's but I have 4.30's in the rear and 38's currently. So its either take the 4.30's out and put 3.73's back in to match the front or leave the 4.30's in and save money to do the front and run 35's.

RedSmokey · Jul 12, 2012

That kind of puts you in a good position imo... After you drop down you can see if you like the 35's and the 4.30's and then change the front to 4.30's if you like it or change the back to 3.73s if you think you will like that better. I drive freeway a lot and unloaded 95% of the time so my 3.73 with the 38.5" tires lets me cruise 80mph or faster at a lower RPM

Snake · Jul 12, 2012

Definitely go with the 3.73's if you drop down to 35's. You're going to be turning some high rpm's at highway speeds if you leave the 4.30's in. My OEM tires were roughly 34" in diameter and the truck had 3.73's. I went up to 37's and 4.30's, and I'm about 100 rpm's higher than stock at 65 mph.

Layson · Jul 12, 2012

What is your goal? Improve mileage? Need new tires? Tired of the look?

Just curious because it may take some serious miles to pay for the gear and lift swap.

RescueF250 · Jul 12, 2012

To be honest Layson my 38's still have 40 percent tread life, I get decent mileage as it is. Idk she's been lifted for 7 years now just looking for a change I guess really. Haven't decide yet.

chappy · Jul 13, 2012

Snake said:
Definitely go with the 3.73's if you drop down to 35's. You're going to be turning some high rpm's at highway speeds if you leave the 4.30's in. My OEM tires were roughly 34" in diameter and the truck had 3.73's. I went up to 37's and 4.30's, and I'm about 100 rpm's higher than stock at 65 mph.

With a 6.0?

jb03 · Jul 18, 2012

Im looking to change gears too. I run 37s and soon 38s. Im thinking about 4.30s. Im wondering if it makes sense to do front and rear lockers at the same time? Good idea or bad?

Thanks