Gear Change

[Lonestar10]

Contemplating a gear change current specs are
CM871 500/1850 - 13sp .73OD - 11R22.5 - 3.36 - Flatbed

Current gear setup for the speeds i normaly run put me at 67MPH at 1600RPM in 12th basically gears have made 13th obsolete.

Thinking about 3.70s so using my 67MPH average

3.36s - 12th Gear - 1600-1625RPM range around 1400 or less in 13th

3.70s - 13th Gear - 1500-1525RPM Range

When i have extra time i cruise at 60-62

3.36s - 12th Gear - 1475-1500RPM Range

3.70s - 12th Gear - 1625-1650RPM Range - 13th - 1375-1400RPM Range

I sometimes kick it up to 70 when the boost gauge is saying its ok

3.36s - 12th Gear - 1675-1700RPM Range - 13th - 1400-1425RPM Range

3.70s - 13th Gear - 1550-1575RPM Range


So thats what im getting on the calc and using my RPM gauge for current gears its about spot on.

and 3.90s seemed a little steep for if i get some flatland crusing.

so what i guess im wondering would the 3.70s be a good investment.

I do run alot of I-80 and other areas with tons of up down hills so im thinking this change could improve mileage as the slightest hill this thing is falling flat on its face vs all these 450HP 1650 or less company trucks blowing my doors off up hills unless their all running around at like 50-60k or less. not saying i really care that they are passing me but when im struggling up a hill and they just mosey on by like its nobodies business its a bit disheartening.


Im not trying to hypermile like some of the champs on here but getting stuff speced to where and how i drive might help payback for the gears. if i gained .5MPG for the engine having to struggle less in the wooptys ied be ecstatic

ill probably do a price check here with i beleive it was Weller. my mechanic is also dealer for i think its Rockwell ill pricecheck through him. i think Rockwell is all brand new parts and Weller is Reman but from what ive heard decent quality on atleast the transmissions that have been posted on it..

Let me know your thoughts and ponderings every criticism and tip helps.

and Rawze youve already yelled at me to get my foot off the floor so were good on that one haha!

[Waterloo]

Doing what you are doing, 3:70's, no question. the 3:90's might be a bit much. I ran the 3:90's years ago in a little Volvo, 8 mpg all day long hauling a light step deck van with a 9 speed, 65 mph was about it, 60 mph was guaranteed 8 mpg. Not something I would want running the mountains.

The 3:70's would be a much better all around gear.

[Rawze]

(05-01-2019 )Lonestar10 Wrote:  Contemplating a gear change current specs are
CM871 500/1850 - 13sp .73OD - 11R22.5 - 3.36 - Flatbed

Current gear setup for the speeds i normaly run put me at 67MPH at 1600RPM in 12th basically gears have made 13th obsolete.
...

http://rawze.com/forums/showthread.php?t...3#pid17353

[Lonestar10]

Thanks for all the information my 370s will be in tomorrow and installed next Friday. brand spanking new rs404 units for 2400 for the front and 1600 for the rear plus whatever labor and fluid comes out to.

[Rawze]

(05-08-2019 )Lonestar10 Wrote:  Thanks for all the information my 370s will be in tomorrow and installed next Friday. brand spanking new rs404 units for 2400 for the front and 1600 for the rear plus whatever labor and fluid comes out to.

nice.

[Magard]

(05-01-2019 )Lonestar10 Wrote:  Contemplating a gear change current specs are
CM871 500/1850 - 13sp .73OD - 11R22.5 - 3.36 - Flatbed

Current gear setup for the speeds i normaly run put me at 67MPH at 1600RPM in 12th basically gears have made 13th obsolete.

Thinking about 3.70s so using my 67MPH average

3.36s - 12th Gear - 1600-1625RPM range around 1400 or less in 13th

3.70s - 13th Gear - 1500-1525RPM Range

When i have extra time i cruise at 60-62

3.36s - 12th Gear - 1475-1500RPM Range

3.70s - 12th Gear - 1625-1650RPM Range - 13th - 1375-1400RPM Range

I sometimes kick it up to 70 when the boost gauge is saying its ok

3.36s - 12th Gear - 1675-1700RPM Range - 13th - 1400-1425RPM Range

3.70s - 13th Gear - 1550-1575RPM Range


So thats what im getting on the calc and using my RPM gauge for current gears its about spot on.

and 3.90s seemed a little steep for if i get some flatland crusing.

so what i guess im wondering would the 3.70s be a good investment.

I do run alot of I-80 and other areas with tons of up down hills so im thinking this change could improve mileage as the slightest hill this thing is falling flat on its face vs all these 450HP 1650 or less company trucks blowing my doors off up hills unless their all running around at like 50-60k or less. not saying i really care that they are passing me but when im struggling up a hill and they just mosey on by like its nobodies business its a bit disheartening.


Im not trying to hypermile like some of the champs on here but getting stuff speced to where and how i drive might help payback for the gears. if i gained .5MPG for the engine having to struggle less in the wooptys ied be ecstatic

ill probably do a price check here with i beleive it was Weller. my mechanic is also dealer for i think its Rockwell ill pricecheck through him. i think Rockwell is all brand new parts and Weller is Reman but from what ive heard decent quality on atleast the transmissions that have been posted on it..

Let me know your thoughts and ponderings every criticism and tip helps.

and Rawze youve already yelled at me to get my foot off the floor so were good on that one haha!

3.70 on 11-22.5 is a nice versatile set up with overdrive 13spd. About the same as 3.55 on low pro 22.5.

[Lonestar10]

yeah driving in wind and rain today 30mph head wind doing 55mph in 11th at 1550rpm still was pulling 20PSI at 62 in 12th bout same RPM was pulling 30-38lbs constantly with 42.5k of manhole castings and lids gross was probably 75-76k loosing fuel weight fast yeesh.