Was planning to run 35s too. I guess the general view is 5.38s or at least 5.13s with a 4dr auto rubicon. I hate that too because I set up my YJ with 5.38s and it bothers me how incredibly small the pinion gear is with that "high" of a ratio. I actually have to replace the rear gears every so often because the pinion teeth develope stress cracks when hammered on repetitively. 5.38s have 43 ring gear teeth and the pinion only has 8 teeth. As compared to 41 and 11 for the 4.10. I guess it's a mute point since the 4.88, 5.13, and 5.38s all have an eight tooth pinion. I guess I'm secretly trying to talk myself into a D60R.

 

all I could think about after I saw my Dana 30 5.13 pinion was how tiny it is and how ez it will snap. I had planned for molly shafts and gussets, c's, and ARBs, etc... But now I think a 44 is a better choice. I dunno. Still doing research and comparing prices.

 

What would RPM be at 75mph with 5:38 and 37" tires? Where can I find the chart?

 

This is a great point, as the gear ratio increases, the teeth on the ring get smaller. I probably would stick with 5.13, and only to 5.38 on a dana 60.

 

37" tires, (measured at 36.5") 5.38s with an automatic at 75mph equals 2565 rpm.

The difference in tooth size is nominal from 5.13s to 5.38s, less than a 10% difference.

 

The ring gear I don't worry too much about. Like was said, the difference is nominal. But when you only have EIGHT teeth on the pinion, one more tooth makes a big difference in how many teeth are actually in contact with each other.

 

I agree and would bring it a step further and tell you that once you go past 4.88 on a D44 the gears are the weak point. (I would go with 4.88) 5.38 is definatly only for and should be in a D60

 

I'm going 5.13's on my manual and doing a Rubi. 44 in the front. Unless the final build cost (chromoly shafts, gussets, skids, etc) comes to something close to a 60 I'll be sticking with the 44.

 

No, the 2169 is at the 60 mph he requested. An auto on 35's with 5.13's runs 2600 and with 5.38's 2725. I prefer the 2725.

 

The new D44's have a bigger pinion geat than 30's and older 44's. It's closer to a 60 in size than a 30.