8.25 29 spline vs. 27 spline illustrated

Its no secret that I like the 8.25 and run them in all of my XJ's. I have seen many posts on here about the differences between the 2 versions of the axle's. I also see many threads about converting a 27 to a 29 and why the 29 spline is stronger.

Today I had both versions in the garage tore down at the same time, the 29 spline was being stripped of its axles to be used as trail spares in my trail rig and the 27 was getting rebuilt for a install in my DD 90'.

The pics are not great but they do show the difference and will tell the tale as to why a 27 spline axle can not be upgraded with out replacing the carrier. Its much simpler to just purchase another 29 spline complete axle. The housings are identical otherwise.

The side gears are the reason the carrier has to be replaced, a 29 spline side gear will not fit into the 27 spline carrier.

The strenght difference is in the shafts themselves, the 29 spline shafts are a considreable amount larger in diameter.

Excellent and the pics are alright for the intended purpose. Now as to the other options 44, 8.8, 9", 60 etc..... what are your opinions and pics????

I know many will disagree with this but I pulled my axles today just to find out if they are 27 or 29 (I have a late 96). They are 29. While I had the axle out, I compared it side by side with D35 and a D44 shafts. To my surprise, the 29 spline 8.25 shaft was identical, if not slightly smaller than the d35 shaft at the smallest part of the shaft (right before the splines). Now I dont know if I got some kind of hybred 27/29 or what but Im not impressed with the 29 spline 8.25 axle shafts. The D44 is markedly larger. And to think, there was a recent thread where people actually said the 8.25 is as good as a D44, whatever.
I wish my mic went higher than an inch, I wouldve measured them.
So whats the deal with the 29 spline necking down so far?

The 44 speaks for itself but if you want disc brakes and a strong axle go 8.8. If money is no object, go with the 9".

The 8.25 is what it is, it will not take what the 44, 8.8, and 9 will. But for the moderate wheeler on a budget, its a good alternative.

If you are running 32" tires and under and are locked/spooled you will be fine with the 29 spline 8.25, 33's if you are open. Gearing options/limitations of the 8.25(4.56:1) should keep you under 33"s anyway.

If you are running 60's, rock on!

Heres a couple pics of the D44, 29 spline 8.25 ans D35 side by side.

center shaft is the 8.25

Ray H said:

Heres a couple pics of the D44, 29 spline 8.25 ans D35 side by side.

Click to expand...

Good pics Ray! The point where the 35 necks down to the splines is the weak point. The 44 is marginally larger than the 8.25.

I like the 8.25, but its still not a 44, C-clips are not a good idea for the trail!

The center shaft is the 8.25.

Ray H said:

Im not sure "marinally" is the correct term unless you think the D44 is only marginally larger than a D35 shaft because the 8.25 is the same if not smaller than the D35 at its narrowist point.
BTW, The center shaft is the 8.25.

Click to expand...

There is no doubt that the D-44 is a better performer for the off-road, but my original intent of the thread was not to debat axles but rather to show those who didn't know or were searching, that the 8.25 27 spline could not be upgraded to a 29 spline with out changing the carrier and that the 29 spline is marginally stronger than the 27 spline.

xjtrailrider said:

There is no doubt that the D-44 is a better performer for the off-road, but my original intent of the thread was not to debat axles but rather to show those who didn't know or were searching, that the 8.25 27 spline could not be upgraded to a 29 spline with out changing the carrier and that the 29 spline is marginally stronger than the 27 spline.

Click to expand...

Of course, my apologies. I'll edit it some if I still can.

Just a note on axle strength and the pics above....an axle shaft is only as strong as it's weakest point which is typically the section with the smallest O.D.

In the case of the 8.25 shaft the smallest O.D is right before the splines which is probably the same as the I.D of the spline root. (This is the best way to make an axle shaft)

In the case of the 44 and the 35 the smallest I.D is actually the root of the spline.

Because of this you can't just compare the shafts diameter along their length. You have to measure the weakest point of each shaft which is typically the diameter at the root of the spline.

Ray H said:

Of course, my apologies. I'll edit it some if I still can.

Click to expand...

Its all good and your pics are awsome!

Thanks for the input!