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FF kit for 14blt SF?

38377k5 said:
28 spline 10 bolt = 1.196"
30 spline 10 bolt = 1.292"
33 spline SF14 bolt = 1.417"
30 spline FF14bolt = 1.5625

Therefore, the SF14 bolt is 45% stronger than a 30 spline 10 bolt and 97% stronger than a 28 spline 10 bolt.

The FF 14 bolt is 48% stronger than a SF 14 bolt, 114% stonger than a 30 spline 10 bolt and 191% stronger than a 28 spline 10 bolt (almost 3 times :eek1:)

All of this is assuming the shafts are made of the same thing and have the same taper and length. I believe that 14 bolt shafts are made of a higher grade alloy than SF shafts (I swear I saw it documented somewhere but have been unable to find it).

Anyway, yes, SF 14 bolt shafts are significantly stronger than 10 bolt shafts but only 2/3 as strong as a FF 14 bolt (assuming they are made of the same alloy). I think you don't see many broken SF14 bolt shafts because there aren't many people that run them, especially with big tires :dunno:
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I'm not sure where your measurements came from, but they are incorrect. The weakest point in any shaft is going to be it's minimum diameter. On a 14BFF shaft the smallest diameter is 1.351 (http://www.pirate4x4.com/tech/billav...ble/index.html, scroll down about 1/3 of the way), while the smallest diameter on the 14BSF is a tad over 1.400. I seriously doubt the SF shafts give up much strength to the FF shafts.

As for a FF conversion, I don't see the point. If you want a FF, get a 14BFF. Don't worry about breaking shafts on the 14BSF - they are seriously beefy. Like others, I have never seen one fail.
 
38377k5 said:
What I'm getting at is this: don't get hung up on the full floating thing. Full floating axles are designed to take the weight off of the axles and transfer it to the bearing hub to increase the weight capacity of the axle. If you are towing heavy loads, full floating axles are where its at. If you are trying to keep from breaking shafts it doesn't matter (other than the material the shafts are made of).
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I know I'm kinda topic stealing but in the same ball park right now. I just got a 3/4 ton truck for $300 and it has a 14sf and d60 8 lug 4.10 gears and the truck has other parts I need compared to my current 1/2 ton setup. I orignally wanted to get a FF but this deal came along and got me... Anyways everyone says the SF is strong but what about with my 39.5x18in. tires? Also keep in mind this isn't a street truck I plan to offroad this thing and eventually put a big block in it... Will the SF even hold up?
 
viperrgh2 said:
I know I'm kinda topic stealing but in the same ball park right now. I just got a 3/4 ton truck for $300 and it has a 14sf and d60 8 lug 4.10 gears and the truck has other parts I need compared to my current 1/2 ton setup. I orignally wanted to get a FF but this deal came along and got me... Anyways everyone says the SF is strong but what about with my 39.5x18in. tires? Also keep in mind this isn't a street truck I plan to offroad this thing and eventually put a big block in it... Will the SF even hold up?
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Umm, a 3/4t won't have a D60 ... and a truck with a 14sf wouldn't have a d60.

Methinks that's your basic 10-bolt Corporate front end.

-- A
 
MaxPF said:
I'm not sure where your measurements came from, but they are incorrect. The weakest point in any shaft is going to be it's minimum diameter. On a 14BFF shaft the smallest diameter is 1.351 (http://www.pirate4x4.com/tech/billav...ble/index.html, scroll down about 1/3 of the way), while the smallest diameter on the 14BSF is a tad over 1.400. I seriously doubt the SF shafts give up much strength to the FF shafts.
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I didn't measure any of the above, its all calculated based on the diametrical pitch of the shafts and their spline count (i.e. its the diameter of the shaft at the splines).

Its true that the weakest and therefore most relevant part of a shaft is the minor diameter.

From what I have gathered the minor diameter of FF 14 bolt shafts is 1.422" which I swear came from Billavista himself, outside of the article. The article is pretty old, I'll try and find that post in the morning.

I would be seriously surprised if SF shafts had a minor diameter as big as their major diameter.
 
viperrgh2 said:
Do they make corp 10 bolt 8 lugs fronts? with manual locking hubs
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quick way to tell if it is a dana 44/10 bolt or dana 60;
is the steering arm held on the knuckle with 3 studs or 4 studs?
is the spring plate on the pumpkin side (right side spring plate, left side retainer) held on with a u-bolt or studs?
 
A couple of comments:

- Whether you can get a the 14SF free or not doesn't really matter if you wanted a FF conversion kit (which doesn't exist anyway), because even if they did exist you would wind up paying at least 5 times as much for the kit then just buying a 14FF to start with. A quick search on the internet brought up prices in the $1,000 range for a D44 FF kit.

- The 14SF is substantially stronger than the 10-bolt.

- For the post with somebody trying to say the SF shafts are any stronger than a FF shaft.......well, they are right and wrong all at the same time, it just depends on how you look at it. The shaft itself (assuming the same diameter and spline count) is the same strength whether it's in a SF or FF configurations. The difference is that in a FF setup the shaft has LESS total forces acting on it. The FF will only see torsional forces, whereas a SF will have the same torsional forces PLUS a bending moment (vertical load) which equals a larger "load" or "force" on the shaft when in the exact same situation as the FF shaft. A perfect example is comparing a 30-spline D60 FF rear axle versus a 30-spline 10-bolt rear axle, the D60 shafts will hold up much better than the 10-bolt shafts even though they are basically the same size.
 
6.2Blazer said:
- For the post with somebody trying to say the SF shafts are any stronger than a FF shaft.......well, they are right and wrong all at the same time, it just depends on how you look at it. The shaft itself (assuming the same diameter and spline count) is the same strength whether it's in a SF or FF configurations. The difference is that in a FF setup the shaft has LESS total forces acting on it. The FF will only see torsional forces, whereas a SF will have the same torsional forces PLUS a bending moment (vertical load) which equals a larger "load" or "force" on the shaft when in the exact same situation as the FF shaft.
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Engineering says that they are totally seperate. If the shaft doesn't fail in shear (i.e. it didn't fail because there is a 1,000,000 ton load on it), the weight on it has absolutely nothing to do with the amount of torque it can transmit before failure.

If a shaft could take 20,000 ft. lbs of torque before failure with no load on it, it would still take 20,000 ft. lbs. to break even if it had a 5,000 lb load on top of it (like a SF axle).
 
I think he might have been talking about something like this originally: http://www.jegs.com/webapp/wcs/stores/servlet/product_10001_10002_761016_-1_10141

They are c-clip eliminators and don't make the axel a FF but rather hold the axel shafts on the outside of the housing rather than on the end of the splines. Basically these are just to prevent a wheel to come shooting off when you're making a hard launch or a warmup burnout at a drag strip or something like that.
 
If your just looking for something to hold the shafts in, do a disk brake conversion.
 
38377k5 said:
Engineering says that they are totally seperate. If the shaft doesn't fail in shear (i.e. it didn't fail because there is a 1,000,000 ton load on it), the weight on it has absolutely nothing to do with the amount of torque it can transmit before failure.

If a shaft could take 20,000 ft. lbs of torque before failure with no load on it, it would still take 20,000 ft. lbs. to break even if it had a 5,000 lb load on top of it (like a SF axle).
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Pretty sure you are wrong...or maybe we are just going down two different roads???

But in any case, when you are calculating the total stress on a component you have to add both the torsional stress (torque) and bending moment (vertical force due to weight on the tire). I have a mechanical engineering degree but it's been quite a while since I did anything like this, so I referred back the "Mechanical Engineering Design" book from college that I have in my desk to verify.

You also have to take both forces into account when calculating factors such as the fatigue life and safety factor. Speaking of fatigue life, this also plays a big role in the SF vs. FF debate. The SF will see more fatigue because of the bending...just like taking a paperclip and bending it back and forth, it will eventually break after you bend it enough times.
 
If you haven't already snapped a 10 bolt shaft, then I wouldn't be too worried about a 14SF, unless you just roll the truck around on the 10 bolts. :)
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i don't baby them, but i try to keep wheelspin/hop to a minimum and i drive wheel a little mor cautiously than i'd like. still, i've managed to kill 3 u-joints in the rear. easy to fix and get back in action fast, though.

I talked to my uncle yesterday. His company (ok, it's only 1/3 his :wink1:) does environmental testing at construction sites, oil spills, etc, so they have to have decently capable 4x4s on some of the jobs. He thinks it may have an aftermarket locker. I'll have to verify that, as well as the ratio, when i get down there.
 
6.2Blazer said:
Pretty sure you are wrong...or maybe we are just going down two different roads???

But in any case, when you are calculating the total stress on a component you have to add both the torsional stress (torque) and bending moment (vertical force due to weight on the tire). I have a mechanical engineering degree but it's been quite a while since I did anything like this, so I referred back the "Mechanical Engineering Design" book from college that I have in my desk to verify.

You also have to take both forces into account when calculating factors such as the fatigue life and safety factor. Speaking of fatigue life, this also plays a big role in the SF vs. FF debate. The SF will see more fatigue because of the bending...just like taking a paperclip and bending it back and forth, it will eventually break after you bend it enough times.
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You have a point there. As the axel shaft spins with the load distributed on top of it, the shaft will deflect some in a sf axel. That is supposed to happen, and my guess is that is why the sf axel shafts are made from a lower hardness to allow the flex. While in a ff axel, the shaft doesn't support any weight and therefore defelcts less that is why GM runs a harder alloy in the FF.
 
Not saying my motor is a powerhouse, but I can't resist flooring that thing every time I drive it, no signs of problems and it was used hard before I got it.

Gov-lock that it came with was broken (stripped gear, acted like an open) and the used replacement gov-lock carrier I put in to replace was staying locked up all the time for some reason, but recently seems to have stopped doing it. That would be my only comment as to weakness on these, the gov-lock. So far, the carrier on the 9.5" diff doesn't seem to be the problem at least, so if you get one with a gov-lock, if it breaks, likely it will keep going, just one wheel drive.
 
viperrgh2 said:
I know I'm kinda topic stealing but in the same ball park right now. I just got a 3/4 ton truck for $300 and it has a 14sf and d60 8 lug 4.10 gears and the truck has other parts I need compared to my current 1/2 ton setup. I orignally wanted to get a FF but this deal came along and got me... Anyways everyone says the SF is strong but what about with my 39.5x18in. tires? Also keep in mind this isn't a street truck I plan to offroad this thing and eventually put a big block in it... Will the SF even hold up?
Click to expand...

As others have said, if it has a SF rear it won't have a D60 front. As for holding up to 39.5's, no problem. You can break a shaft if you try hard enough, but it would probably be a situation where a FF shaft would break as well (i.e. a totally bound up tire and you hammer the p!$$ out of it).
 
38377k5 said:
I didn't measure any of the above, its all calculated based on the diametrical pitch of the shafts and their spline count (i.e. its the diameter of the shaft at the splines).

Its true that the weakest and therefore most relevant part of a shaft is the minor diameter.

From what I have gathered the minor diameter of FF 14 bolt shafts is 1.422" which I swear came from Billavista himself, outside of the article. The article is pretty old, I'll try and find that post in the morning.

I would be seriously surprised if SF shafts had a minor diameter as big as their major diameter.
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I measured the SF shaft myself when I had mine apart, so I am confident of that figure. I have never personally measured a FF shaft so all I have to go by is the BV article.
 
Chevy305 said:
You have a point there. As the axel shaft spins with the load distributed on top of it, the shaft will deflect some in a sf axel. That is supposed to happen, and my guess is that is why the sf axel shafts are made from a lower hardness to allow the flex. While in a ff axel, the shaft doesn't support any weight and therefore defelcts less that is why GM runs a harder alloy in the FF.
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The outer half of the axle shaft is more than 1.600" in diameter, being 1.700 at the bearing surface. If you took 1.400" (the shaft's minimum diabeter) out of the center the resulting hollow tube would still have no problem supporting the axle's GAWR. IOW, this does not limit the torque capacity of a 14BSF axle shaft.

The selection of material for a SF shaft isn't based on it's ability to flex - 4340 and others will flex a lot more than the low alloy steels before yielding, and it will resist fatigue as well. The main reasons that dictate the material used is cost; low alloy carbon steel can be inexpensively carburized to a fairly high hardness. This is needed since the bearing runs directly on the ground axle surface. I am not sure what material a FF shaft is made from, but my guess would be medium carbon steel of moderate hardness, similar to what is used for most production steel crankshafts. Alloy steels are much more expensive, and I doubt they would be used in an application where a bit more cross-section of much less expensive steel would accomplish the same thing. I don't believe there is any real limitation to using 4340 for a SF shaft, but the heat treat would be complicated, driving up cost.
 
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