Best gear ratio for Dana 30 front and Dana 44 rear?
- Thread starter Jaime Rangel
- Start date
Except they mesure out at 36. The calculation site you frequent just cant handle everyone's rig setup every time.
No. Your tire measurement is incorrect or your reporting of 75mph at 3k rpm is incorrect. The math is accurate to the information provided.
He might just be rounding up a tad or speedo just slightly off. Most 37’s are 35.5”. 35.5” comes to 2910 at 75.
I know what he is doing. I also know the math has been explained multiple times and in multiple ways, which tells me where the computational problem really is.
I changed your tire size to an 36" for the new image above. The calculator site I gave the link to above is dead-nuts on no matter what transmission, gear ratio, or tire size. It has all the transmissions and their ratios built in. As an rpm calculator and not just a chart it's 100% accurate and reliable.
You didn't actually run the numbers did you? Change it to 34.02".
Just to make sure, The rear tire is closer to 35.5 now.
Listen Jj, I'm not here to buck your proven system. I used these same calculations 15 years ago with my first TJ, they were too high for my needs. I ended up having to size up from 33s to 35s on 4.56 because of the recommendation. I enjoy driving my jeep differently than you do, I enjoy working with my manual gears on the rocks. I'm here to explain my setup and what works for my rigs.
Last edited:
I understand, let's for moment think I'm telling the truth. There is still a fairly large gap in what you are calculating. You think the disconnect is in my GPS and my jeep gages? Picture is there of the tire.
The calculator is correct for the information being entered into it. What is incorrect is your assumption as to what the result ought to be. Pay more attention to the explanations that have been given.
Measure from ground to hub and multiply by two to get your rolling diameter. There are multiple ways to calculate it but it turns out that measurement is a very good rule of thumb and very easy to do.
Measure your speed with GPS not with speedo.
Andy
We will call that 2975rpm at 76.1mph.
Your 37s have an effective rolling diameter of 35.23". Enjoy!