JK vs JL Dana 44 "D44" axle shaft comparison.

[Crawdad1028]

I had seen a pic of this a while back but couldn't find it when I was looking for it so today when I had the chance I snapped one just to throw it out for anyone who was curious. JK Dana 44 vs JL M220 rear axle shafts. JK left - JL right

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[mwilk012]

Holy shit. That's quite something.

 

[TrailTorque]

Obviously the smaller of the 2 is the JK.. Duh.

 

[Crawdad1028]

Which is which? I have my assumptions but just looking for confirmation

JL is the larger one on the right.

 

[TrailTorque]

JK D44 vs JL D44HD

JL +1 lol

 

[Crawdad1028]

Honestly can't tell much from that photo. What are the spline counts and diameters?

I was in a hurry and didn't measure diameters but I believe the JK is 30 spline and the JL is 32 spline

 

[vavaroutsos]

Yeah...stnd. D44 is 1.3125" diam 30 spline. Pretty sure the JL D44 is larger diameter and definitely 32 spline.

The splines are the same size and diameter is proportional to circumference. Therefore:

JL diameter = JK diameter * 32 / 30 = 1.4"

 

[D60]

Is that true for *all* gear hob operations? Not in my wheelhouse so I'm curious. Is the 1.4" a published spec or just extrapolation?

x2. Were they shooting for 1.4" or 1-7/16"? ie 1.4375?

 

[vavaroutsos]

Is that true for *all* gear hob operations? Not in my wheelhouse so I'm curious. Is the 1.4" a published spec or just extrapolation?

There's no fundamental reason the splines need to be the same size, but it's my understanding that Dana/Spicer use the same size splines and just vary the number of splines with different axle sizes. So you can count on an axle with more splines being larger diameter.

 

[Crawdad1028]

Some Tech from Billa Vista:


Diametrical Pitch

Diametrical pitch of splined shaft is a specification that relates the number of splines to the size of the shaft. This spec is what allows us to refer to an axle as just "35 spline" and be able to compare it to a "30 spline" axle without having to also list the minor and major diameters of the shafts. For example, almost anyone would instinctively tell you that a 35 spline shaft was stronger than a 30 spline shaft. But what if the 35 spline shaft had a minor diameter of 1 inch and the 30 spline shaft had a minor diameter of 2 inches? I can tell you without doing the engineering math that the 30 spline 2' shaft would be stronger. To avoid this confusion, and indeed to insure that the number of splines and the size of the shaft are standardized so that the teeth are evenly spaced and parts can be made to fit together, we have the concept of diametrical pitch. We are familiar with the fact that there are a limited, set number of standard threads-per-inch available that match certain bolt sizes (e.g. a 3/8" bolt has either 16 (coarse) or 24 (fine) threads per inch) so that we may have a reasonable chance of finding nuts and bolts that fit together - can you imagine if the number of different threads per inch for any size bolt were unlmited?!! In the same way, splined shafts must have a limited number of possible diameter and # of teeth combinations. Instead of threads-per-inch, diametrical pitch is used.

The pitch diameter of a splined shaft is is the mid-point between the major and minor diameters. The diametrical pitch is the number of teeth per inch of pitch diameter, similar to the number of threads per inch specified for bolt threads. Because the splines are all the same size and shape, the distance between the centerline of adjacent splines (the circular pitch) remains constant. Therefore as the pitch diameter of the shaft increases, more teeth can "fit around" the pitch diameter, and therefore the larger the shaft diameter the larger the number of splines for any given diametrical pitch.

An actual diametrical pitch specification will be a number specifying the number of teeth per inch of pitch diameter. Industry standards state that most modern automotive axle shafts (All of the 28, 30, 31, 35, 40 spline axles that interest us) are 24-pitch. Therefore, if the shaft had a 1-inch circular pitch diameter it would have exactly 24 splines (or teeth). Using this standard diametrical pitch of 24-pitch a 35-spline axle has a major diameter of 1,500 inches; a 40-spline 1.708 inches.

Note that if you know the diametrical pitch of a splined shaft you can calculate its major diameter. This may be counter-intuitive, as it may seem as if one would decide to use a 1.5" diameter shaft, and then decide to cut splines into and settle on 35 splines. This is not how it actually works, In reality, the pitch controls the major diameter, as the following equation demonstrates. Using the eqation you can calculate the number of splines on any size shaft or conversely the size of any shaft given the pitch and number of splines.

Major Diameter

Do=(N+1)/P

Where:

Do = major diameter of splined shaft
N = number of splines
P = diametrical pitch (24 for just about every axle we care about)

If you know any 2 of the 3 variables you can simply re-arange the equation algabraicly and compute the third/

For example:

Q: What is the major diameter of a 35 spline shaft?

A: N=35, assume P=24, Do=(N+1)/p = (35+1)/24 = 36/34 = 1.50"

I'd post a link, but I'd bet the mod here would delete it.

That is a lot of information! My brain hurts a little now.

 

[Crawdad1028]

Also I should add that this is the JL shaft used in the photo. They're are not bulletproof. Lol

 

[Chocolate Thunder]

Also I should add that this is the JL shaft used in the photo. They're are not bulletproof. Lol

Know what happened to it?

 

[Crawdad1028]

It came out of the rubi axles that I swapped into my sport. The Jeep that they came off of sees a lot of east coast wheeling with heavy headlocks and 37s. He upgraded to tons to better suit his needs. I’ll be running 37s on them but don’t expect to have much issue with my wheeling style. I’ll upgrade to chromos when they’re available.

 

[Crawdad1028]

They don't look horrible. I'd run them, but I'd also invest in spares.

Are the JL rears centered so the shafts are interchangeable; i.e., one spare rear shaft?

Unless I am mistaken the shop owner who did my swap said the jl shafts are in fact equal length. I went ahead and replaced the twisted one, and as soon as chromos show up I’ll swap them out and keep these as spares.

 

[tCub]

Interesting! Anyone have any idea the difference between Sport/Sahara 30/35s JK to JL? Similar increase in size?

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