Gear ratio!!!!

i have heard of these setups for years

my dream is to get me an pre-egr classic, to this day, but if i could verify your story, i would jump on my dream truck TODAY

sometimes i think we believe too much of the company-hype and forget that we are the captains of these ships

 

I have a 12.7L Detroit with 13 speed tranny and 3.55 rear end gears and low pro 22.5. Final drive ratio on tranny is .87 and 12th gear is 1 to 1. I run I-20 from Dallas, Tx to Louisiana speed limit is 75mph. At 65mph I’m running 1700rpm. 70 mph is 1800rpm. If I changed my rear end ratio to 2.93 would that lower my rpm? Will I still have enough pull power to pull a few hills?

 

Man that's high....are you sure about those rears? I have lower gears than that and turn a lower rpm. That should not be. Either your gear ratios are off, or the transmission isn't an overdrive.

What HP is your Detroit? If it's 500 from the factory, it is up to task for just about any load you want to pull (80000 or less) and still get decent economy.

 

It’s a 430 Detroit. The truck had a automatic tranny and it went out so the 13speed was put in its place

 

That makes sense. No offense meant, okay?

IMO, the 430 Detroit SUX. I don't care much for the old 470 either. In fact, I couldn't tell the difference between a 430 and a 470. But the 500...awesome. The best all around engine for OTR 48 period.

If you had a 500, I would look into changing the gears. The 430, I wouldn't, because it's prone to falling on its face in a hill climb. I would almost wager that a 500 with your current setup with do 1 mpg better than the 430.

 

What makes no sense? That the old tranny was a automatic and it was replaced.

 

You misread my response.