Dana 44 stock MJ Gear Ratios

[coolwind57]

Anyone have stats on Dana 44s throughout the MJ years--specifically about gear ratios?  Are automatic for 1990 showing up as 3:55 or 3:54 ratios?

 

How the heck can one tell a 3:55 from a 3:54 by rotation?! 

 

I bought a D44 "with 3:55 ratio" last night and after cleaning up today, I can make out 3 54 on the tag.  I pulled the cover and the ring gear last digits are 46-13, which comes up as 3:538.  Looks like I just bought a 3:54 to match up to my 3:55 front D30.  I should had pulled the cover-- but is this even a concern?  Can I match this up with my 3:55 front diff D30?

 

I searched here but only found some comments regarding this on other sites.  What's your thoughts on this, fellas?

 

Just for kicks, here's a couple comments from another Jeep forum:

 

Dude #1:

"Don't be alarmed if you see 3.54 on the gear. It's basically the same as the newer 3.55, they just started to round up."
 

Another dude said:

3.54 and 3.55 will work together but they are different.
A 39 tooth ring with an 11 tooth pinion is a 3.55.
A 46 tooth ring with a 13 tooth pinion is a 3.54.

So the 3.54 has a bigger pinion and is thereby a somewhat stronger gear set.

 

[Pete M]

3.54 and 3.55 are essentially the same thing.    comes down to the number of teeth the particular axle has and how you want to round. 

 

the ratio is the teeth on the ring divided by the teeth on the pinion. 

 

46 and 13 gives 3.538

39 and 11 gives 3.545

 

same thing with 4.09/4.10/4.11

 

45 and 11 gives 4.090

41 and 10 gives 4.100

37 and 9 gives 4.111

 

[Minuit]

Sometimes, the gear tooth counts work out that way. For all intents and purposes, they are the same.

 

For what it's worth, 39 divided by 11 equals 3.5454545454... repeating forever. 46 divided by 13 equals 3.53846 and so on. That's a 0.19%, or just under a fifth of one percent difference. The factory didn't think that was enough of a difference to matter, and neither should you. Run them together without worry.

[coolwind57]

Thanks, fellas.  

[Dzimm]

Good info above.  Just wanted to throw it out there, differences in tires and tire wear would also have a similar affect on "effective" gear ratios.  Have you ever seen two different brand tires on a 4x4 vehicle?  Those aren't the exact same size even though the numbers are the same.

 

It's basically splitting hairs when it's that close.

[derf]

The threshold is if they are within 1% you're good to run th together.  A 4.09 Dana 44 works fine with a 4.11 Dana 30.  A 4.27 Dana 44 works with a 4.30 Ford 9".  3.55 and 3.54 gears work fine together.