Gear ratio calculator

[Liftr]

I found a website that has a comprehensive calculator to compare every combination of Transmission, transfer case, differential, and tire sizes.

Not sure if a cross posting is allowed, but here is the link:
”Grimmjeeper” dot com

http://www.grimmjeeper.com/gears.html

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[Artsifrtsi]

I found a website that has a comprehensive calculator to compare every combination of Transmission, transfer case, differential, and tire sizes.

Not sure if a cross posting is allowed, but here is the link:
”Grimmjeeper” dot com

http://www.grimmjeeper.com/gears.html

I’ve been asking about the same thing... I thing everyone just uses a W.A.G method for gearing.

 

[Liftr]

In the drop down menu, the transmission is listed as a “Dodge 850 RE”.

No more guessing required!

 

[Artsifrtsi]

In the drop down menu, the transmission is listed as a “Dodge 850 RE”.

No more guessing required!

Yep, I found that. The big thing, is when I enter numbers for the stock 32's and 3.73, and second column go with 37's and 4.10, my numbers are about the same. So according to the calculator, to be slightly better geared than where I am right now, I need 4.10's (bumps the RPM at highway speed about 100). 4.88's, which is what people here commonly say is required for 37's, spins up the RPM almost 1000 at highway speeds. 4.56 bumps RPM up about 500.

 

[Liftr]

Yep, I found that. The big thing, is when I enter numbers for the stock 32's and 3.73, and second column go with 37's and 4.10, my numbers are about the same. So according to the calculator, to be slightly better geared than where I am right now, I need 4.10's (bumps the RPM at highway speed about 100). 4.88's, which is what people here commonly say is required for 37's, spins up the RPM almost 1000 at highway speeds. 4.56 bumps RPM up about 500.

I agree. On the chart, I see 109 RPM difference at 70 MPH.
I did a screen shot for ease of comparison.
The chart on the left is ”32’s and 3.73”
The chart on right is “37’s and 4.10”

 

[wanderer]

There was a chart that gave the tire size gear ratio rpm at certain speeds on the jl forum couple of years ago wish I could find it

 

[Bbannongmu]

This is a good site to see side. I am going a bit deeper than the chart says to offset heavier tires and added weight from rock rails etc.

 

[Liftr]

There was a chart that gave the tire size gear ratio rpm at certain speeds on the jl forum couple of years ago wish I could find it

This calculator does allow you to change tire size as a variable, also.

 

[BEERviper]

Wow this is a big help, thanks @Liftr!

I'm up in the air about 35's vs 37's and whether I will need to regear the ecoDiesel with all the added torque over the Pentastar. At least with this I can see the different engine RPM at different speeds with bigger tires and gear combinations!

 

[brog]

There was a chart that gave the tire size gear ratio rpm at certain speeds on the jl forum couple of years ago wish I could find it

I know I'm late to this thread, but is this what you were looking for?

 

[wanderer]

Yep pretty interesting if you look at 37s@70 and see the rpm then go to the horse power torque curves which as i recall is pretty flat I don’t think that there is a lot or hp lost

 

[wvyankee2]

Chart is not correct for the Gladiator. Are the Transmission gear ratios different form the JL? I'm about 2350rpms on 35's with 488's.

 

[cgflyer]

I know I'm late to this thread, but is this what you were looking for?

This isn't accurate for the JT MT either, with 35's at 70 in 6th gear, I am at 2,000 RPM even. I'm about to put 37's on without a re-gear...not many doing it with the MT that I can see, tons doing it with the AT without much complaint. I will likely re-gear, but seriously doubt I will go 4.88. Heck, based on this chart, the 4.10 with stock 33's isn't even the "performance" gear.

 

[wanderer]

Another sure if the gear ratios are the same. Seeing how this is mathematically derived value I would expect some difference
Considering wind resistance inflation rolling resistance exta weight etc. but. I do agree on the autoseems like it is 400rpm off

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