TexasFireF150

yall makn me want to regear so bad. Have the 3:55s right now with 35s and I got a custom tune and it helped but want to see if I can get some fuel economy back. I do a lot of highway driving still. Would yall think I would get better or worse fuel economy going to a 4:10 with my 35s???

cbr600rx7

With 35s and your big lift I would go 4.56s with out question. It's a safe bet that you will gain SOME MPG back because you are way out side the intended power band since the 6R80 has a double over drive already.

35s make your 3.55s act more like 3.31s. If you wanted to be close to stock then 4.10s would get you close but with the extra weight and lift 4.56s would be my guess for your application.

Keep in mind the raptor came with 4.10s from the factory on about a 34 inch tire but also had the grunt of the 6.2. That should give your prospective.

WXman

Complete waste of time and money to ever go up only one "size" in axle gears. You'll never even know it was done.

jp360cj

I have to disagree. 3.73 to 4.10 is definitely noticeable. Been there, done that. And although it won't be as noticeable in 6th gear, it will make a bigger difference in lower gears.

Also, in many axles 3.73 to 4.10 is a 2 "size" jump, with something around a 3.90 in the middle.

TexasFireF150

So for the best highway economy running a 6" and 35s you would think a 4:10 swap ? Having the overdrive will let me drive 80mph and not be too high of RPMs?

SteveLord

I think I gained around 200-300rpms at 70mph. At 1900-2000 I believe. That is from 3.55 to 4.11 gears. 5.0 and 34" tires weighing 66lbs each. 4 inch lift.

If there was a 4.30ish option, would have done that. The 4.56s seemed a little much for me for my daily driver.

TexasFireF150

awesome, thats kinda the information I was lookn for. I was thinking 4:56 was a little much for daily driving.

cbr600rx7

Care to explain how it's a "complete waste of money"

People upgrade from 3.31s to 3.73s all the time. It's a very common upgrade in the mustang world and in the truck comunity. 3.31 to 3.73 is a 0.42 increase in gear ratio or about 13% as pointed out in this thread. 3.73 to 4.11 is a 0.48 increase in gear ratio or about a 11% increase in ratio. That's what I would consider significant.

I have personally gone from 3.42s to 3.73s in a GM 12 bolt and I can say even the 0.31 change was noticeable. I have also driven 3/4 ton chevy work trucks (350 vortec/4L80 combos) with 3.73 and 4.10 gears and can personally say the 0.48 increase between the two is noticeable.

And TexasFire150: with your set up 4.56s are probably best. 4.10s would put you close to your stock rpms. However you have a lot more mass, wieght, and rolling reactance to over come. Think about it for a second, your factory tires probaly weigh about 30lbs each. With your 35s I am willing to bet they are 65+ lbs each. Now consider your truck is probaly 8 inches taller and has more wind restance to over come to maintain the same speed as before and you will get what I am saying. While 3.55s to 4.10s are noticeable increase I think if you plan on running 35+ tires on your rig 4.56s would be way better suited. If you need a comparison look at the factory raptor and older powerwagons and look at what gears and tire sizes they came from the factory with compared to your set up. The ford 6.2 and ram 5.7 make a little more low end grunt compared to the 5.0 as well. Just something to consider.

Yes it's not a huge change but since I never plan to run more then a 32-33 inch tire and tow in the mountains it may be worth while. Also if I dropped the front LSD upgrade my cost would be about $1500 out the door. I don't even think you can buy a set of good long tube headers for the 5.0 for that price or convert to a boss manifold. So bang for buck this may actually be a good performance mod especially for the guys who tow or the 2WD 1/4 mile guys.

So please explain how it's a waste of money.

TexasFireF150

ya Im back and forth between 4:10s and 4:56. Just still wanna drive 80on the highway and get 15mpg ha.

WXman

Please see post #26 in this thread.

In my experience, a 150 RPM difference is undetectable on the tach, much less to the seat of the pants. You're getting effectively zero gain. But what you are doing is dropping serious cash to pull off the swap, and then you're opening yourself up to new cans of worms such as having gear whine, vibrations due to a faster spinning driveshaft, longevity (which is a function of having the preload set perfectly), etc.

To me, it's just not worth it. And, that's a .38 increase in ratio, not a .48 increase.

By all means, if you think you're already set on doing it...go for it.

Yes, people do it all the time. I myself went from 3.27 to 3.73 on my Mustang and it didn't get me any more than about one tenth of a second at the track. I've done 4.11s and 4.88s on 4x4s and picked up no measurable gains whatsoever...just a much lighter wallet.