Regear for MPG?

You will never get good fuel mpg running acert over 1400 rpms. I have an acert also and I love it. It has a 10 sp tranny with 3.42 rear and 22.5LPI keep the rpms little below 1300 which is like 60mph i get over 7 hauling 45k. There is another guy on here with same engine n trans but with 3.25 rear he's getting 6.5 - 7mpg. He keeps the rpms where I do but he is able to go 65 - 70mph thanks to 3.25.

 

yea once i did the math, hammer down makes more sense for you. (although i rarely come to that conclusion) Fass, and muffler shouldn't effect dpf. Does cali not let you change mufflers? fass def wont change anything. Sounds like you are on the right trac to saving fuel. If your gonna sell the truck, i wouldnt mess with the gearing since 3.55 is easy to sell.

 

3.25 AND a 13/18B trans will net you the best MPG's and driveability, do the trans first because the 10 speed is not going to like the 3.25's (and neither will you). There is a guy on here named Cowpie has 2.64's and a 18 spd behind a Detroit getting excellent MPG's but you have to really drive the truck, no setting the cruise and holding the steering wheel. What size drive tires are you running? That has some impact in your gear selection.
http://big-rig-road-speed-calculator.blogspot.com/2011/03/semi-truck-road-speed-calculator.html
That is a handy little tool if you decide to re-gear/swap trannies. Actually if your '08 Acert is bone stock your doing pretty good (a lot better than most).

 

I did the 18 spd with 2.64 rears in my glider. So far, not a bad thing, but then I am using a Series 60 engine. I pull both heavy and light. The Acert likes a little lower RPM than a detroit for mpg. Now, one can go about this a little differently. Instead of either running in direct with a tall ratio like 2.64 or in the top hole with 3.55, select a rear ratio that you can run in comfortably one gear down, in 17th. The first overdrive is not as parasitic as the double overdrive top hole. If you want, you can use a road speed calculator I have if you have MS Exel spreadsheet and plug in various rear ratios, tire rotations per mile, transmission gear ratios to your heart's content and find out what would be the best combination for your needs. PM me with an email I can forward it to you.

 

I have the same rears and trans on a c12 and I have to run 57-60 to get 7mpg. 65mph I get 5.8-6.2

 

Sounds like LP22.5's I've got the exact same motor tranny combo, but I have LP24.5's and I run 100 rpm less than you at the same road speed. 1400 @ 65, 1500 @ 70. My truck has 1.1 million on it and starting to show her age, if I decide to rebuild instead of replace, it will be 18spd/3.25s or maybe 3.08s I like Cowpies 2.64 idea but I'm not sure the Acert is going to like the tall gears when I'm off road.

 

Honestly I don't mind going 60 but new rears and a 13 or 18 would be nice. I just wish I could split 9th and 10th my turbo has some bad lag so I have to wind 9th out for 10th to pull.

 

If you are running lp22.5 on the drives and are only going to keep the truck another year, your cheapest option is going with standard 11R22.5 on the drives. You will run at nearly the same rpm as lp24.5's and you won't have to buy new rims.

Of course, you could run a little slower, say 65 mph or under.