What are G2 Dana 44 rear axles made of?

[imahnu]

So with OEM spline ARBs do I get much of an advantage moving to chromoly shafts? I moved to 35s a few years ago and started doing harder trails (Moab Trifecta last October) and started thinking about more preventative maintenance. I have stock 30 front and 44 rear with 4.88s and ARBs. I only turn on the ARBs when I need to (and rear way more than both) and stay light on the gas. It's a manual so sometimes I need to hit it a little. Are the shafts worth the expense? Any expense is better than the bill to be towed out of Moab.

In short I’d say definitely on the 30 and the 44 would be a good idea.

 

[mrblaine]

That makes a lot of sense now. Thanks for taking the time to explain that! I was completely unaware of the interaction between the unit bearing and the stub shaft. Good information to have.

How does that change with the use of something like Yukons 30 spline stub free spin kit?

It changes completely since the stub is full floating and dependent solely upon the strength of the splines and shaft to transmit the torque to turn the wheel.
Fun fact- we actually made a set of stubs to fit unit bearings long before they were a product. We took a set of Warn 30 spline stubs, annealed them, had them machined to match an OEM stub and then had them heat treated again. My buddy didn't want to do a hub kit which is the only way we could get stronger shafts early on.

That clamping force is why we see more than a few RCV stubs twist off. Oddly, they called out a very low torque number for the spindle nut, something along the line of 100ish ft lbs. That isn't enough to provide the friction needed so they twist off inside the unit bearing.

 

[1999TJGreen]

In short I’d say definitely on the 30 and the 44 would be a good idea.

I wonder if the better twisting ability of the chromoly shaft actually might offset the fact that the spline size in the ARB would be stock. As Bruce Lee said “Notice that the stiffest tree is most easily cracked, while the bamboo or willow survives by bending with the wind.” Do they make bamboo shafts?

 

[mrblaine]

Nice to know my recent failure is a statistical anomaly! G2 chromoly, FWIW.

I wasn't going to spend the time to type that out but now I have to. We've seen a lot of those type failures. They are almost always import shafts. Early on, Alloy USA had a big problem with that. If you were to spend some time to forensically examine the problem, I suspect you would find at least two things that are incorrect. The first is the splines were not cut deep enough to let the flat shoulder butt up with the correct amount of clamping force against the back of the unit bearing. The second is a poor heat treat. The smooth face of the twisted off pieces tells you the heat treat was almost non-existent.

If you look closely at the face of that shoulder that is supposed to butt up tightly to the back of the unit bearing, you will likely see very little evidence of being clamped tightly. There should be high evidence of shear or some slight galling showing that it was forced to move under high load and I'll bet little of that is there.

The key point I left out above is "done correctly" delivers what we see in the OEM stuff and violations of that give us your problem.

 

[imahnu]

It changes completely since the stub is full floating and dependent solely upon the strength of the splines and shaft to transmit the torque to turn the wheel.
Fun fact- we actually made a set of stubs to fit unit bearings long before they were a product. We took a set of Warn 30 spline stubs, annealed them, had them machined to match an OEM stub and then had them heat treated again. My buddy didn't want to do a hub kit which is the only way we could get stronger shafts early on.

That clamping force is why we see more than a few RCV stubs twist off. Oddly, they called out a very low torque number for the spindle nut, something along the line of 100ish ft lbs. That isn't enough to provide the friction needed so they twist off inside the unit bearing.

Hmm that would make me wonder then if the Yukon kit is stronger than RGAs 30 spline us made kit with the 27 spline stub.

If there’s a virtually zero fail rate then why the need, other than disconnecting your driveline would you worry about the 30spline stubs?

 

[mrblaine]

Hmm that would make me wonder then if the Yukon kit is stronger than RGAs 30 spline us made kit with the 27 spline stub.

If there’s a virtually zero fail rate then why the need, other than disconnecting your driveline would you worry about the 30spline stubs?

There are virtually no failures that twist the stub off inside the unit bearing. The failures occur at the holes for the u-joint caps in the yokes.

 

[imahnu]

There are virtually no failures that twist the stub off inside the unit bearing. The failures occur at the holes for the u-joint caps in the yokes.

I think I’m gonna switch my plans for using the 30 Spline RGA kit and run that with the unit bearing instead of Yukons kit. Use that money for changing my rear bumper and tire carrier.