Rubicon TJ D44 Front Axle XJ Swap

Since TJ owners convert to a high pinon d30 from a XJ and its a direct bolt on, would a D44 front axle housing from a Rubicon TJ be of an advantage to swap on the front of an XJ? Since you can now find many Rubicon Axle housings on ebay i thought this might be a good time to upgrade to match my D44 Rear?

If it's free yes. If its $1500 like most absolutely not. There have been many many discussions about the Rubicon front d44s...search

I agree w/Basalt.


But I personally would give the Rubi 44 more credit than most guys do...Especially when you only plan on running 33s w/said rig. (Like me)

A rubi 44 would be primo in my situation, and I'd buy one if it were 5-600. But not what I've been seeing them go for. (1500+)

hjeepxj said:

I agree w/Basalt.


But I personally would give the Rubi 44 more credit than most guys do...Especially when you only plan on running 33s w/said rig. (Like me)

A rubi 44 would be primo in my situation, and I'd buy one if it were 5-600. But not what I've been seeing them go for. (1500+)

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Why?

Same shafts as a LP/HP D30.

Same knuckles, brakes, ball joints as a LP/HP D30.

HP D30 R&P is about the same strength as a LP Rubi D44.

HP D30 has better prop shaft angles.

What's the advantage?

Hell of a lot of work just for larger carrier bearings.

r@m

Root Moose said:

Why?

Same shafts as a LP/HP D30.

Same knuckles, brakes, ball joints as a LP/HP D30.

HP D30 R&P is about the same strength as a LP Rubi D44.

HP D30 has better prop shaft angles.

What's the advantage?

Hell of a lot of work just for larger carrier bearings.

r@m

Click to expand...

A lot of work?

Its a bolt in....it comes with a selectable locker and the 4.10s I want....

Root Moose said:

Same shafts as a LP/HP D30.

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I believe the inner shafts on the Rubi 44 are 30 spline and from there on out it's regular D30 stuff... right or no???

JEEPZZ said:

I believe the inner shafts on the Rubi 44 are 30 spline and from there on out it's regular D30 stuff... right or no???

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Yes - 30 spline inners, D30 outers.

not hi-jack but.....
30 spine inners / 27 spine outers, which u joints would they share? 297/760's?
-g

hjeepxj said:

A lot of work?

Its a bolt in....it comes with a selectable locker and the 4.10s I want....

Click to expand...

I stand corrected on the spline count but still...

Can you get the Rubi axle for cheaper than an ARB and R&P install? Not likely. Every complete Rubi axle ready for install I've seen for sale is over $1400 or so - most much more.

I still think the shaft angle that comes with a HP D30 is more important than any "advantage" a Rubi D44 has - especially if you have a NV242 t-case (my bias).

$0.02

r@m

I bet if you bought a selectable locker/gears/and alloy shafts you would have spent the same amount of money as a rubi 44, but have a HP30 that is stronger and geared deep enough to wheel big tires..

Root Moose said:

I stand corrected on the spline count but still...

Can you get the Rubi axle for cheaper than an ARB and R&P install? Not likely. Every complete Rubi axle ready for install I've seen for sale is over $1400 or so - most much more.

I still think the shaft angle that comes with a HP D30 is more important than any "advantage" a Rubi D44 has - especially if you have a NV242 t-case (my bias).

$0.02

r@m

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That was my point, so Id probably never end up with a Rubi 44, but if there WAS one for 600$, id run it. :shhh:

hjeepxj said:

That was my point, so Id probably never end up with a Rubi 44, but if there WAS one for 600$, id run it. :shhh:

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Hell, for that price I'd buy it and put it in the pile with the rest of the parts I have hiding in my barn for when I get around to building a SWB Jeep.

Good score!

r@m

I'ld buy it for $600, sell it for $1200. Tell the guy he's getting a great deal, and put the money into the hp d30

GPRSDLYT said:

not hi-jack but.....
30 spine inners / 27 spine outers, which u joints would they share? 297/760's?
-g

Click to expand...

Yep - 760's

Root Moose said:

Why?

Same shafts as a LP/HP D30.

Same knuckles, brakes, ball joints as a LP/HP D30.

HP D30 R&P is about the same strength as a LP Rubi D44.

HP D30 has better prop shaft angles.

What's the advantage?

Hell of a lot of work just for larger carrier bearings.

r@m

Click to expand...

About the R&P. You said it's about the same strength? How so? Isn't a Dana 30 7.2" vs 8.5 in a Dana 44? Or is the Rubi special? What about tube size? 2.75 vs 2.5?

:flipoff:

mikedashg said:

About the R&P. You said it's about the same strength? How so? Isn't a Dana 30 7.2" vs 8.5 in a Dana 44? Or is the Rubi special? What about tube size? 2.75 vs 2.5?

:flipoff:

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Tube size is the same for an HP Dana 30 and a Rubie 44.
There's VERY little, if any, strength difference between a HP D30 and a LP 44. The HP design is stronger in the forward direction. R&P strength is really a moot point anyway. You almost never hear of someone breaking a R&P. Usually, the U-joints go, and those are the same for both axles. I'd MUCH rather build a HP 30 than a Rubie "44". The high pinion more than makes up for the 44s larger carrier bearings. :thumbup:

BillR said:

Tube size is the same for an HP Dana 30 and a Rubie 44.
There's VERY little, if any, strength difference between a HP D30 and a LP 44. The HP design is stronger in the forward direction. R&P strength is really a moot point anyway. You almost never hear of someone breaking a R&P. Usually, the U-joints go, and those are the same for both axles. I'd MUCH rather build a HP 30 than a Rubie "44". The high pinion more than makes up for the 44s larger carrier bearings. :thumbup:

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What? Then what was the point! Seriously, what the heck we're they thinking. If you're going to put a 44 in somthing, why couldn't they put a regular one it, that actually REALLY WAS plenty stronger then the 30. What a waste.

:flipoff:

I totally agree!
The ONLY advantage I see to a Rubie 44 is that the range of gear selection is greater, and if you get a complete one you have a nice selectable locker. To buy just a housing to run 4:88s or higher, it's not worth it IMO.
The Rubie 44 IS an upgrade to a TJ Dana 30, as both are LP. I had a LP 30 from the factory in my 2001, and decided to build a HP 30 from a '94 XJ instead of a Rubie "semi-44". The Rubie 44 would've cost alot more for no real advantages, and I'd lose driveshaft angle and ground clearance compared to a HP30.

mikedashg said:

About the R&P. You said it's about the same strength? How so? Isn't a Dana 30 7.2" vs 8.5 in a Dana 44? Or is the Rubi special? What about tube size? 2.75 vs 2.5?

Click to expand...

Just to make this point clear for anyone else that stumbles across this thread.

The high pinion (HP) Dana 30 uses reverse spiral gears. This means that the gears are specifically cut to run in a front axle application and the loads on the gear faces are "optimized". For more detail on what that means pick up a machine design text book at your local library. It's been 12 years since I did my mechanical engineering degree so I forget/muddle the specifics and don't dare engage in a conversation about this on the specifics. 12 years of earning a real living as a computer geek will do that to you.

Anyway, a low pinion (LP) axle drives the gears in the wrong (i.e. weak) direction when used in a front axle application. Some say this is anywhere from 20%-30% weaker than driving the gears in the correct direction.

A reverse spiral gear pair driven in the correct direction are 20%-30% stronger (depending on source cited, metallurgy or specific gears, etc.) than a LP gear set run in the incorrect direction.

Some say the D44 LP is ~20-30% stronger than the D30 LP. A HP D30 would be ~20%-30% stonger than the LP D30.

So, this roughly puts the HP D30 used in a front axle application at a very similar (if not stronger) data point compared to a LP D44 used in a front application.

For most people (note use of word most), the HP D30 is more axle than you will ever need in a front axle. That's not to say the HP D30 doesn't suffer form some more issues compared to a LP D44 (carrier flex leading to diff failure chiefly) but again, very few people will ever encounter that.

My advice: if you are planning on running "normal" 35 inch and smaller tires then the HP D30 is probably a reasonable choice. By normal tires I mean BFGs, GY MT/Rs, etc. Big heavy tires like a Swamper or Bogger in 35" (or larger!) will probably be hard on a HP D30. Hell, I wouldn't run a real LP D44 either if it was my truck. Tires that size/weeght really deserve a HP D44 or HP D60 if you want a "fire and forget" kinda Jeep.

If you really want a LP D44, try to get one that has D44 scale parts through out (brakes, shafts, etc.).

Just my spin.

$0.02