Dana 30 Axle and Gear Axle Ratio Question

[TJim]

Hey!


I am a little bit confused about my front dana 30 axle. My VIN equipment listing mentions that I have a Dana 30/186MM Front Axle.

On the contrary, in the service manual (2004 TJ) it is listed as 181 FBI (Model 30) Front Axle.
Is there a difference between 186 vs 181 Dana 30, or is it just a typo?

Also, the Vin equipment listing mentions: 4.11 Rear Axle Ratio.
The Gear Ratio is the same between my front and rear diffs or not?

 

[Chris]

It's just a typo. You have a Dana 30 front axle just like any other TJ.

Yes, the gears are the same between both front and rear axles. If they weren't, very bad things would happen when you put it in 4WD.

 

[TJim]

1) So I have a Dana 30 181MM, the 186MM is just a typo in the Equipment Listing.

2) Yeah I know that they have to be exactly the same, but it just felt weird that it mentions specifically REAR Axle Ratio 4.11.

Thanks Chris!

 

[Jerry Bransford]

Yes the front axle has a 4.10 and the rear has a 4.11 which is ABSOLUTELY not a problem. They are .01 different because the front Dana 30 and rear Dana 35 or Dana 44 have different ring gear diameters and manufacturing constraints cause that difference.

It's not an issue because on the street you're in 2wd and the front axle isn't being driven it wouldn't matter if it was 3.07 in the front and 4.88 in the rear. Offroad the lower traction allows the front and rear axle to slip against each other so the .01 difference is a non-issue there too. Virtually all standard Wranglers have the .01 ratio difference between the front and rear like 3.54/3.55, 3.73/3.74, and 4.10/4.11. Only the Rubicon has matching front and rear Dana 44 axles so their ratios match exactly.

 

[Ryderbike1]

I realize this is a few years old now and you’ve probably already sorted it but I figured I’d share what I’ve found for others. Dana 30/181 or Dana 30/186 refer to what side of the Dana 30 carrier break it’s on. 181 is 3.55 and lower gears and 186 is 3.73 and up gearing.

 

[CharlesHS]

The difference in the 181 and 186 carriers: 181 mm is 7.125 and 186 mm is 7.323 is a difference of .198

 

[TheBoogieman]

WARNING! Nerd alert.