Regear for MPG?

13 speed will probably help more than a gear change. Plus will really help with resale. If you swapped to to 3.42 or 3.36 that 10 speed will probably cost you mileage unless your really light loads. getting up to speed on long grades will take its toll...Id guess a trans swap would cost similar too. most likely the ratios of OD will be close so there wont be any difference in rpm but youll be about half the drop in rpm between shifts..just my option, others with a lot more CAT experience should trump any of my opinions.

 

Go read some of the articles Pittsburg Power puts out about gearing, I think they are working on a plan of put a 2.64 or similar in a truck with an 18 speed and then just not using the overdrive gears.

I think if you gear it too low, with the OD, it will lug the motor and actually hurt your milage.

Mr. Haney may have some knowledge on this also.

 

You would probably be money ahead to trade it off and buy something set up better for what you are doing. The optimal gearing for an Acert is 3.36 with a 13 or 18spd.

 

There are tons of options to improve MPG. Kevin Ruthiford has a lot of info on this topic, but there are a lot of small cheap things you can do before going for a gear swap out. Running in a 6x2 config with a 2.64 gear ratio will allow you to use trailer tires on one set of drives and drives on the other. This will decrease rolling resistance and resistance form 2 difs. That configuration will also allow you to run your trans in direct, not OD to decrease trans drag. Yes a better gear ratio will help, but exhaust all your other options first since this is pretty pricey. (at least that was KR's advice to me)

Pittsburgh Power mufflers (.5 mpg) about $300 bucks for 2 and even cheaper if you buy the one not re branded by PP. BY FAR THE BEST 300 YOU WILL SPEND
Fass System. (.33mpg) $685 also available at PP, but probably cheaper else ware.
Airtabs. (unknown) Yes they look stupid, but they certainly decrease rain on mirrors and stability in wind, so they must be doing something. $200
Supper Singles (.5+mpg) ~$4000 Dont know if you have a problem with Singles, but my Xone Line Energy D's save me .5-.75 over the duels I was running. Please don't start a debate on suppers vs duals, but I like them. The fuel saving pays for all the negatives imo.
Wheel covers (.1-.2 mpg) $200 These are what you see on shnider trucks. They cover your wheels to help your aero
Micro Blue bearings. (.4 mpg) $950
KR Scangadge (up to 30%) $185 Shows life info on how much your spending, average mpg, average over last 8 sec....helps you see how to drive more efficiently.
Side skirts on truck (>.5mpg) Varries

At 70 MPH aerodynamics are hurting you more then the drive train or anything else. Making sure your truck is as aerodynamic as possible is important. A few hundered pounds of chrome may look nice, but every pound counts on those up hills. Also leave your tires chains home when not in season.



Do you own the trailer? If so, Aero flex skirts save about 7% fuel and tail cones save 4%. $4000 investment for both. Singles on the trailer will save .3-.5mpg.



I know you don't want to hear this, but running 65 instead of 70 makes a huge difference. Obviously on a 3000 mile trip this adds about 2 hours to your trip, but if you get 6.3 instead of 5.8 mpg, you would save $163 @ 4/gallon. Wow that's not as much of a difference as i thought. For 163, bucks, keep the hammer down lol. (it would be worth a try to see how much of a difference it actually makes) Also, try to take min fuel possible over the rockies. If you can take 200, and only take 100 over, that's an 800 pound savings going up those hills. All aluminum wheels helps a little to.

 

Yea if he changed the rear gearing I'd want to upgrade to a 13 or 18. Either would work just fine, although the 18 has a lower low for getting off the line. In any case with a 2.64 you would run in whatever gear is dirrect. On a 10 speed though, i wouldn't want to loose the extra gear. On a 13 or 18, its not so bad. One thing i didnt mention is switching to bigger tires. Much cheaper then a gear change and gives the same effect.

 

What are we talking here, whats your rpm at 65 and whats your rpm at 70.