Can anyone dumb this down for me?

The more splines - the stronger it is...

Wouldnt more splines mean that theyre getting smaller? The size of the shaft doesnt get any bigger, as in like a super ___ kit...

Kind of like gears, the lower you go, the more teeth are on the ring, the smaller they are, the weaker they are....

Or am I missing something (probably :laugh: )

not sure about the super kits, but most of the time the more splines there are, the larger the diameter of the axleshaft
the reason why gears get weaker as the ratios get lower and lower, is that the pinions get smaller and smaller as they have less teeth, and that is typically what will let go with really low gears

the more splines there are on the shaft, the less strain there is on each spline. the rotational force being applied on the shaft is distributed amongst each spline evenly.....therefore the more splines, the less force on each spline therefore theyre less prone to breakage.

While it's true the splines are getting smaller, it has to do with dividing the load into smaller parts. Let's straighten the thing out and explain it this way...

You have a rack 1" long, and you are going to use it to "stop" a load of one ton (2000#)

If you have ten teeth on the rack, you have a load of 200# on each tooth.
If you have twenty teeth, reduce that to 100# each.
You see the progression already...

Without going too far into metallurgy and stress analysis, you are creating a larger safety factor when you reduce the load per spline by having more splines, assuming you are using the same alloy and the same heat treat. That's essentially why you want to increase spline count - it's like increasing overall tooth count on a gear system - you can split the load over more teeth and reduce the load per tooth. You can get away with more on a splined shaft because there is more area under stress (and therefore less stress per unit area) then there is on gear teeth, but you have the idea.

Of course, the best solution for increasing the strength of a spline engagment setup would be to use LONGER splines and more mating area, but that is not always an option.

Also, when there are more splines, they are made shallower - which makes the "core" fo the shaft effectively larger and increases the cross-sectional area of the shaft - increasing the area under stress and reducing the load per unit area. It's a similar effect to going from a 1" shaft to a 1.5" shaft - there's more area to "share" the load and you have a system that is stronger. Think like you have to squat 200# on one leg - then do it on two. You'll get the idea.

5-90

here is a pic of a 31 spline Dana 60 axle shaft next to a 35 spline Dana 60 axle shaft from Moser, notice the size difference
hope the pic works

It's all so clear now! :cheers:

Also, the super kits do increase the shaft diameter. The super 35 is a 1.31" 30 spline which is the same as a 44. Same with the super 30 kit.

Heres a thread that has some info on the super 44 shaft sizes.
http://www.naxja.org/forum/showthread.php?t=36941&highlight=super

another method of thinking is total area. the area is increased with more teeth, thus spreading out the load more.

olivedrabcj7 said:

the more splines there are on the shaft, the less strain there is on each spline.

Click to expand...

Exactly, but there is also a point of diminshing returns. 31 splines is stronger than 21 splines, but if someone tried to make a driveshaft with 331 splines, in a diameter appropriate for an XJ, it would probably be weaker, not stronger. So, the more splines the less strain, up to a point. The manufacturers, of course, are careful not to go beyond that point.

diameter typically increases with number of splines, that's where most of the strength comes from. obviously there is a balance between too many splines and too few; if you had 1000 splines on a 1.5" shaft it would be like sandpaper.

a good example of this is comparing a D60 with a 14bolt. both have full-float with 30 spline shafts, but the 14bolt is WAY stronger, because it has 1.5" 30 spline shafts, and the D60 has 1.31" 30 spline shafts.

most of you guys are missing one very critical detail. axle spline is a constant. usually 35º or 45º with the same depth. in order to increase the spline count you have to increase the diameter. a 33 spline super shaft for the dana 44 is about .125" larger in diameter than the stock D44 shaft.

generally, yes.

but like I pointed out 14bolts and D60s have 30 splines, but the 14b is 1.5"and the D60 is 1.31. Also, some older Dana axles of 1.31" diameter have crazy 19(?) spline stuff.

did the 8.25 get larger diameter shafts when it went from 27 to 29 splines?

hjeepxj said:

The more splines - the stronger it is...

Wouldnt more splines mean that theyre getting smaller? The size of the shaft doesnt get any bigger, as in like a super ___ kit...

Kind of like gears, the lower you go, the more teeth are on the ring, the smaller they are, the weaker they are....

Or am I missing something (probably :laugh: )

Click to expand...

Most automotive splines (trans and coarse splines excluded) are like an extended spur gear (very simple involute form gear) - but the standard is a 40 pitch - so as your spline count increases each spline stays fairly similar in size but the overall diameter and your contact area + torque load capacity increases...

The 30 degree pressure angle and involute tooth form just allow the parts to transfer torque along the pitch diameter (mid point of the spline face) plane rather than at the root or crest of the teeth (manufacturing tolerances would be too costly to make each set matched and then you would loose the interchangability precision)

HTH

Matt

ive done some major research but can figure it out.

can anybody tell me how maybe splines are on axle out of a dana 44 on a scout 2?

thanks

dave

30 splines, like most modern D44's.

IUPxj94 said:

ive done some major research but can figure it out.

can anybody tell me how maybe splines are on axle out of a dana 44 on a scout 2?

thanks

dave

Click to expand...

Dave -

Think smarter not harder - I found warn's info in ~ 2 min

Inner or outer axle? - the inner (side gears) should be 30 spline - the stub shaft would likely be the fine spline ( 27or 30 IIRC) if it was an external - 5 large bolts holding the hub on - the internal hub stuff should be the coarser spline with only the internal lock ring holding the hub on - That is 19 spline - say 79' wagoneer like mine...

1974-1983 WAGONEER Disc/Drum (Length 9.94 in.; 19 Spline;Left;Right) 38815 warn #

Matt

Your apps:

1971-1980 SCOUT II (Length 32.91 in.; 30 Spline;Left) 38790 warn#
1971-1980 SCOUT II (Length 14.69 in.; 30 Spline;Right) 38808 warn#

1972-1980 SCOUT II (Length 8.72 in.; 30 Spline;Left;Right) 38248 warn #
1972-1980 SCOUT II (Length 8.72 in.; 27 Spline;Left;Right) 39105 warn#