Just how tough is the old D44 10 spline?

Thanks all for the help related to the axle retention question earlier. I tried searching for other posts on the axle on here and other boards.

It seems alot of folks dont particular care for these old axles given the other options out there, but just how tough are these little things? There must be reason they served on the M38s, and they dont really seem to be a problem to service. I mean I understand that a 30 spline has more contact mesh surface and 1 piece, but is it THAT much stronger?

Anyone have any experience that relates to the resilience of the D44 tapered? I understand that 33-35 max tire can be had on them, but I just plan to run the standard military NDT in 30 x 7 x 16" rim. Nothing hardcore offroad, just mud and normal woods terrain.

 

Depends on engine, torque multiplication through the transmission/transfer case, driving style, tire size, terrain encountered, weight of vehicle, and condition of rear axle assembly.
A simple upgrade is to convert to 19 spline axle shafts or convert to full float axle shafts. The 19 spline shafts are significantly stronger than 10 spline shafts. 30 spline shafts are significantly stronger than 19 spline shafts. This is due to the load distribution being less on each individual spline and that part of of the shaft the greater the spline count.

One of the important issues is the tapered axle shaft spinning in the hub shearing the axle key. If installed correctly and the axle to hub nut is kept torqued properly they hold up fairly well up to 33" tires. Over that is overtaxing the tapered axle Dana 44 IMHO.

 

Thanks. Its a 55 CJ5. Terrain to be encountered is mentioned above. Nothing too crazy. Just bottomland hardwoods and the occasional mudhole in Louisiana. I dont have the luxury of mountainous terrain down in the swamp

 

Am running a Dauntless V-6, t-14, D-18. Was running a tapered axle 44 with 33's for about a year with a loc rite. Would consider myself an easy on parts driver. Twisted both axle splines about 3/8", one finally broke right at the carrier. They did last a lot of years though. After all, they are over 50 years old.

 

If it's a stock '55, we are talking about an F-134. I imagine that it would be pretty hard to hurt the axles with that engine.

 

Dana 23-2 rear, Dana 25 front and Dana 27 front all have 10 straight cut spline axle shafts.
They measure 1.12" outside diameter or .005" under 1-1/8".

Dana 30 front has 27 rolled spline axle shafts.
They measure 1.162 outside duiameter.

Pre 1957 Jeep Dana 44 rear axle shafts all have 10 staight cut spline rear shafts.
They measure 1.225" outside diameter.

Post 1956 Jeep Dana 44 rear axle shafts all have 19 involute spline axle shafts.
They measure 1.245" outside diameter or .005" under 1-1/4".

Post 1970 Jeep Dana 44 use 30 count rolled spline axle shafts.
They measure 1.285" outside diameter.

A 4 cylinder Willys engine with 8-1/2 or even the HD 9-1/4" clutch will be hard pressed to break a 10 spline D-44 unless it is obviously abused.
The developed (engine) and delivered (clutch) torque is simply too low to break an axle shaft.

The worst thing you can do is spin a tire at high speed on some slippery surface then suddenly gain full traction.
That creates a condition called "SHOCK LOADING" where inertia (wheel spin) exceeds the axle shaft shear strength.

 

Although alluded to above, it is more the diameter of the shaft than the actual spline count that determines the strength. And as Ken noted, more splines=bigger diameter. While 19 spline are an improvement, if stock you still have the keyed, tapered hub, which usually gives way even before you shear a 10 spline axle. I wouldn't spend money on a 19 spline axle/side gear set.

Two options for 30 spline:
1) Find one of the 701/2-71 uber rare 30 splined, flanged axles or
2) Full float the existing housing with one of Herm's 30 spline kits.

Kind of a toss up which is stronger because those full float kits taper to a 27 spline drive flange, but they also are not supporting the weight of the vehicle like the flanged version does. And if you do break an axle shaft with the full float, unlike the flanged setup, you still have wheels and brakes on it.

 

I had one customer break 3 short side Dana 44 10 spline axles in one year with otherwise totally stock drivetrain. Certain people can and will break anything. I have also seen a couple 300+ HP sbc Jeeps that never break anything. It really is all about the operator.

 

My brother had a '49 with a built 327 in it. I had to rebuild the T90 twice and replace the ring and pinion once.(they had a 1949 date on them so they could have been a bit tired)
Axle shafts were fine.

 

So why is it that the short side usually break first? The only explanation I can come up with is the long side maybe has more torsion twist available before failure.

I ran a pretty healthy 327 on a completely stock 10 spline 44 for a couple of years in my B and didn't break anything. The tires/wheels were the factory H78-15's off my CJ5. I think the driver is the key to whether or not the stock axle will survive.

 

Yep, that sounds right. Higher strain per unit length makes fatigue more likely.