Change rear gears or go to 11R24.5?

Yeah I'm out of New Jersey I run out your way a bunch. The hills on 80 is def a good place to save fuel splitting gears. The RTLO 13s is what your going to like the best. They have a bunch of different models the only difference is the torque ratings. 16913a,18913a,20913a, all of them are basically the same model just the first two numbers define their torque ratings. Normally the higher the torque rating the higher the price. But not always the case. The RTLO part is important that's low inertia. Translates to finer teeth smoother shifts. I'm not an expert on transmissions I'm sure others could help you. However, I've done a lot of research on this b/c I changed from a 15spd to 13spd two yrs ago in one of my tractors and spent a lot of time learning about the new technology out there. I'm an old school guy so I had to learn about trans all over again. Any of the models I listed above will do what your looking for. All have the same final drive .73 so top speed will be the same. Hope this helps you a little.

 

Final drive is 0.73 on the 13 and 18 speed. The 10 speed zinnita says he has is a direct drive tranny. 1.00 final drive.

 

Not sure if this is true, but I heard 24.5 tires are getting kind of hard to find. I drove a Freightliner with a 500, S60 Detroit, 13, and 3.55 on 22.5's and that thing did just fine @ 70.

 

[QUOTE="semi" retired;4022221]Not sure if this is true, but I heard 24.5 tires are getting kind of hard to find. I drove a Freightliner with a 500, S60 Detroit, 13, and 3.55 on 22.5's and that thing did just fine @ 70.[/QUOTE]
Tall rubber 24's can be a challenge on the road(ie truck stop chains)but most larger truck tire retailers still stock em--24 low pros are typically readily available--but again since a majority of the larger carriers are all 22 low--most of the typical truck stops etc carry more of these.....
Now to the OP--do whatever--buy whatever you want..not gonna get into that debate,,,But--if your goal is fuel mileage exclusively --Long hood 379 w/an accert is NOT the way to go..oh and BTW--I have owned driven Long Hood Pete's EXCLUSIVELY since my first 82 359--would want anything else....
And lastly--do yourself a favor--and get/request oil samples form them--TMC--from what I understand does a pretty good job w/their PM programs--but--all the truck on their site are relatively high mileage--and PROPER CAT rebuilds are NOT cheap...
Just my $.02

 

the specs must be off on those trucks, with a 13 , 3.55 rears and lp 22.5 I turn 1300 at 62 mph, if you are going to run 70 with that c15 you aren't going to get fuel mileage. why not just leave the low pros and simply slow down??

 

I read post #4
I guess I cant understand how someone who is just becoming an owner /op, and is driving for a company at the moment can think that fuel mileage is not important.

if you are worried about the longeveity of engine buying one with 900,000 on it with time sensitive freight isn't the way to go in my opinion. cause rebuilding could be sooner than later

and running one of those cats at 1500 with 22.5 lo-pro and a 13 speed will get you 72 mph, but that acert will love the fuel pump at that speed and rpm, the acert is a different cat than the other kitties, I love mine pulls great , but I keep her at 1275 to 1300 at 60 to 61 and average right at 7 get up to 72 and I am in the 5 range , at todays prices, from 7 to 5 mpg is about 23,500 dollars worth of fuel in one year on 100,000, well enough and have vacation money left to get a platinum at the cat shop with head and turbos.

not worrying about fuel mileage and owning a truck is like Chinese to me I cant understand it.

I think you just think at the moment you aren't worried about mileage and have been blinded by a black and chrome peter car, I hope that freight you are going to pull pays over well over 2 bucks a mile both ways, you are gonna need it.

that's just my perspective, from owning one a while. olhand you gave solid advice also.

perhaps you should look at some other trucks instead that are spec more to your drivetrain requirements

 

Skateboardman is kinda missing the question I think. You want the truck to run 68-72 mph and not have the truck winding out all day and night. Running 62 mph does not answer the question. You will get 7 mpg at 72 mph with the right set-up for the c-15. If he sets the truck up to run between 1275-1350 rpm at 70 mph. He will keep the motor where it likes to run and get best mpg with the least wear and tear on the motor which is his goal. The speed limit in the majority of Texas is 70-75 mph, 62 mph will make him look like a fleet truck out there. Gearing the truck correctly is everything.