Rear end ratio 13 speed 3.21 rear ends with 11R 24.5 rubber. ISX 2350 500 hp. I usually run in 12th with the cruise set on 65 this puts me right around 1500 rpm. I thought it would be Ok but I don’t really like the tall ratios. What would you guys recommend I go to if I changed the rear ends? 3.42 3.55 3.73 ? I generally operate on two lane roads and a little bit OTR. On flatland in the plains usually about a 350mile radius of Garden City KS. Loaded 80,000 lbs looking to go maybe 90,000 Lbs. Appreciate your advice.
I would go 3:90... The 3:90, I ran a little Volvo with a nine speed with 3:90 gears in the flats, 65 on cruise, 8 mpg all day long, but I was hauling light loads in a step deck van. I miss that truck. And I wish I had a set in my current truck, running through the mountains here in PA, and it is embarrassing.
If you look around on here , rawze has posted a calculator several times that will tell you the rpm at which speed depending on ratio .
Personally I would gear it to run at 1650 at 65 mph if thats what you like to run at .
But thats just me ...
3.90 would be about 1500 rpm at 65 I believe.
I also had 18 speed in all my trucks though , I did have one 15 speed actually.
What would RPMs be with same rears, low pro 22s, 65mph in 13th.
Ive got 3.36s behind an 18 hauling up to 100k. When in Louisiana i cruise at 60ish (55 limit) in 17th(12/9 direct) @1450rpm with ease. In Tx i cruise 68ish in 18th (13/9over). The only problem ive ever had in a 13 with same gear ratio and load is the gap between 5 direct and 6 direct. My opinion. If ur rears grenade and u have to replace em go with a 3.55, otherwise ride the 3.2x.
i replaced in my lonestar 3.36s with 3.70s this gave me 65 1500 70 1600 75 1700rpms with 11r 22.5s. cost was 6 grand for brand new center sections.
(10-25-2020 )the missing link Wrote: [ -> ]If you look around on here , rawze has posted a calculator several times that will tell you the rpm at which speed depending on ratio .
Personally I would gear it to run at 1650 at 65 mph if thats what you like to run at .
But thats just me ...
3.90 would be about 1500 rpm at 65 I believe.
I also had 18 speed in all my trucks though , I did have one 15 speed actually.
I think you were referring to this..
http://rawze.com/forums/showthread.php?t...3#pid17353
btw: forum memeber 'the missing link' is a career super-B, heavy hauler. He knows what he is talking about.