Forum advice vs shop advice: Are 5.38 gears to low for Dana 44?

[Jerry Bransford]

I forget the details, but aren't the RGA 5.xx pinions the same size as 4.88?

I can't say if they're the same as 4.88 but RGA's 5.38 has the same diameter pinion gear head as the 5.13. I didn't notice a size difference between my previous 4.88 pinion gear & the 5.38 that replaced them but then I was too busy to compare them all that closely.

 

[Jerry Bransford]

5.38 is numerically higher than 4.88... that’s the nomenclature I was taught by dad. Maybe being a stubborn engineer factors in to it too

Of course it is numerically higher but 5.38 is still a lower ratio than 4.88. Better to refer to it being a higher or lower ratio than to confuse everyone.

 

[Mike Jolley]

5.38 is a lower ratio than 4.88 is. A lower ratio causes the ring gear to rotate at a lower speed with the same speed at the driving pinion gear which is why it's called a lower ratio.

And a lower ratio doesn't necessarily mean it doesn't mesh adequately for the forces involved. There are plenty of people like me running ratios like 5.38 in our Dana 44 axles on extremely difficult rock crawling trails without problem. They have been well tested on extreme level trails like the Hammers out in Johnson Valley California.

I revised my post to reflect Jerry and Chris' gear terminology to avoid adding confusion. It's a confusing enough topic without that (sorry dad).

 

[Rob5589]

From a pure gear ratio standpoint the 5.38’s match well with a 35” tire behind the 42rle with that tall 0.69:1 overdrive ratio. The 4.0 likes to run in the 2500-3000 range at freeway speeds. Listen to Jerry, speaking from real world knowledge is always better than listening to somebody that makes assumptions. If you plan to wheel it hard you have one other factor to consider and that is gear mesh. The lower the gear ratio the less gear mesh you will have, that’s just the physics of a ring and pinion gearset. Everything else being equal, the 4.88 gears are stronger than 5.38’s because they have more gear surface touching. My rear end builder prefers not to use anything lower than 4.88 in a Dana 44. For 5.38’s you might want to step up to a Dana 60 or something else with a larger diameter gearset. We run 4.88’s in my sister’s TJ rolling on 33” rubber. I was hesitant to go that low with the relatively short tires but it actually does extremely well on the highway. At 80mph GPS on the way to the Rubicon last month she was still turning less than 3000 rpms. Generally too fast to ever drive a lifted TJ but I wanted to see where things went.

Meh, the only gear set we ever saw that had issues due to pinion size was the Richmond gear 5.71 for the Toyota 8". That tiny pinion mixed with 35+ inch tires caused issues. We would recommend the 5.29 instead and even as small as it is, we did not experience any issues like the 5.71. We installed plenty of 5.57 in the 8.5" Chevy diffs for guys running 36-40 inch tires and experienced no issues. Your guy not wanting to go lower than 4.88 is based on what? What would he prefer in something smaller like the Dana 30?

What you will generally find is guys that gear low are running harder than those that don't. There are plenty on this forum that run 3.07 and "mild" trails while those running lower ratio's are running "hard" trails. It only makes sense that those "hard" trail guys are running their rigs quite a bit harder and will experience more failures.