30 spline shafts have a slightly larger diameter than 27 spline shafts so they are stronger, everything else being equal. But up front, hardened (like 4340) chromoly 27 spline shafts are plenty strong enough for 35's and any kind of a locker. That's what I installed into my previous TJ and they held up well.Just coming back to this thread to ask one more question!
A reliable way to run a locker in a Dana 30 (even with 35" tires) is to use (as @Jerry Bransford has suggested in various threads):
I am wondering, which is the purpose of 30-splines axle shafts for Dana 30? Can anyone elaborate on this?
- 4340 chromoly 27-spline axle shafts
- Spicer 5-760x u-joints
I get it! So just to recap!30 spline shafts have a slightly larger diameter than 27 spline shafts so they are stronger, everything else being equal. But up front, hardened (like 4340) chromoly 27 spline shafts are plenty strong enough for 35's and any kind of a locker. That's what I installed into my previous TJ and they held up well.
Going with 30 spline inner/outer shafts would require also installing a very expensive conversion to 30 spline manual hubs. I'm aware of no 30 spline unit bearing hubs available that will hold up. Milemarker made them at one time but they weren't up to the job. If anyone knows of a 30 spline unit bearing hub for our TJ Dana 30/Dana 44 axles that'd be good to know.
Yes our Rubicon front axles use a 30 spline inner shaft but its outer stub shaft is still an unhardened 27 spline.
It’s an option for unnecessarily emptying your walletI get it! So just to recap!
1) All I need are 4340 chromoly 27 spline shafts (27 inner/27 outer).
This way I will not need anything additional like manual hubs! Correct?
2) 30 spline axle shafts (30 inner/30 outer) would need a conversion to 30 spline manual hubs.
Would 30 inner/27 outer shafts be an option? In this case would a conversion to manual hubs needed?
**Sorry for the many questions but at this point I could say that it's all Greek to me. But I speak Greek, so I will say that it's all Chinese to me.
30/27 can be run without a manual hub. That’s what Rubicons came with btw.The 30 inner/27 outer? Okay!
Would this require a manual hub though? or not?
Can you point me into a manual hub conversion kit? or tell me roughly how much it costs?
I am just asking out of curiosity
I am not exactly getting confused.30/27 can be run without a manual hub. That’s what Rubicons came with btw.
@Irun is our current small hub conversion expert. I know nothing about them because to me; it’s adding unnecessary failure points. K.I.S.S......
Is it possible your getting confused because of the rear axle 27 to 30 spline upgrade?
The axle shafts between front and rear are very different (aside from ujoints). The rear starts at a larger diameter near the wheel hub, then tapers much smaller at the diff with 27 splines. The front maintains the same shaft rod diameter all the way from the ujoint ears to the diff.
The rear known failure point is where the shaft tapers down in size. We fix this by going to the larger diameter and larger spline count.
The front axle only needs this kit and it’s ready for 35’s
Actually I came up with those:It’s an option for unnecessarily emptying your wallet
Hey Jerry, can you please let me know why the 30 splines inner / 27 splines outer are cheaper than the 27 inner/27 outer? (See my above post)As above, I would stick with 27/27 spline hardened chromoly shafts, like 4340. Again, 27 spline hardened front axle shafts are plenty strong for 35's and a locker. Changing the spline count from what the factory installed would require 1) a replacement 30 spline carrier, locker, or LSD and 2) different 30 spline hubs.
You don't need 30 spline shafts up front for 35's and a locker. I ran 27 spline 4340 inner/outer shafts for years on some occasionally very tough trails including my second trip through Sledgehammer in Johnson Valley. My first trip through Sledgehammer broke a factory front axle shaft.
27 spline 4340 hardened inner/outer shafts are a direct drop-in replacement for the unhardened carbon steel 27 spline shafts the factory installed.
Like either of these...
10 year warranty imported: https://www.revolutiongear.com/prod...ep_tj_xj_yj_wj_27_spline_kit_discovery_series
Lifetime warranty American made:
Either would be a great choice.
No idea, those links just take me to the front webpage.Hey Jerry, can you please let me know why the 30 splines inner / 27 splines outer are cheaper than the 27 inner/27 outer? (See my above post)
Am I missing anything?
I am planning to install a selectable locker at the same time. So I don't have a problem with the carrier. It will be replaced.No idea, those links just take me to the front webpage.
Keep in mind, as said above a couple times, that you MUST match the spline count of your differential and your hubs. Your Dana 30 differential/carrier is a 27 spline device. Your hubs are 27 spline devices.
You cannot install 30 spline inner shafts because their diameter is too physically big to fit into your Dana 30's 27 spline carrier.
Again, you do not need 30 spline shafts up front. 30 spline shafts have a big advantage in the rear but you do not need 30 spline shafts up front. The front shafts never see more than about 50% of the load seen by the rear axle shafts.I am planning to install a selectable locker at the same time. So I don't have a problem with the carrier. It will be replaced.
I am aware of that. But thanks for reminding.
Sorry, I should have mentioned that before. Is this changing your perspective? Since a NEW locker is going to be installed at the same time as shafts, should I install a 30 spline locker, with 30 splines inner /27 splines outer shafts?
For two reasons:
2) To be able to upgrade in the future to manual locking hubs. By just replacing the outer shafts to 30 splines and keeping the same inner shafts?
I don’t have yeild strength number for the 2 shaft sizes. But my experience with 27/27 tells me the housing will fail long before either size shaft is an issue.For two reasons:
2) To be able to upgrade in the future to manual locking hubs. By replacing the outer shafts to 30 splines?
They are very handy to have if you break a locker, carrier, some axle shaft breakages, or if your pinion angle is slightly off due to caster setup and it's causing front driveshaft u-joint vibrations on the highway.IMHO, manual hubs are a thing of the past and add zero value to a TJ