NP241 / Ford NP205 Strong Box Doubler

[Behemoth DT]

----------------------------------SAE 4340--------SAE 8620-------SAE 4130

Modulus of elasticity---------------29,700 ksi ------29,700ksi-------29,700ksi
Tensile strength (annealed)--------108,000 psi------77,800 psi------81,300psi
Yield strength (annealed)----------68500 psi--------55,900 psi------52,300psi
Hardness (annealed)---------------96 RB------------80 RB----------82 RB
Tensile strength (normalized)-------195500 psi-------91,800 psi-----97,000psi
Yield strength (normalized)---------125000 psi ------81,800 psi------63,300psi
Hardness (normalized)--------------112 RB ----------90 RB----------93 RB

Source:
http://aeonmaterials.com/alloys.aspx

[BoondocK5]

Originally Posted by Behemoth DT

4130 has a slightly higer TENSILE strength, and considerably lower yield strength than the stock 8620, but still not even close to 4340.

Originally Posted by Behemoth DT

Please explain it to me, and the others that have used 4340 shafts for this very application for years.
If anything, the real life fact that there have only been 2 or 3 broken DD shafts, should trump any speculation.

I've made the correction in my post, I re-read my emails from RCV. The shafts are made from the much coveted 4340. Besides, regardless of what it is made of, RCV has a lifetime guarantee against breakage. Thats saying something in this business.
Why not just post up who is doing the heat treat for you? And be done with it.

[Behemoth DT]

Originally Posted by BoondocK5

I've made the correction in my post, I re-read my emails from RCV. The shafts are made from the much coveted 4340. Besides, regardless of what it is made of, RCV has a lifetime guarantee against breakage. Thats saying something in this business.
Why not just post up who is doing the heat treat for you? And be done with it.

I sent them an email. I'm sure they won't mind, but I'd like to get the "all clear" from them before I post their name. Also, I'm going to do some type of a lifetime warranty on shafts as well, whether they will warranty them or not. I agree that a lifetime warranty on the shaft is a must.
DD said that he had like a 1 year warranty, and someone broke a 6-7 year old shaft, and he replaced it at his cost.
My 6 month limited warranty on the shaft was originally for the resplined shafts. I'm glad that I got away from resplined shafts.

[MaxPF]

While I'm at it, I will rip apart your dumb-assery in this post:

Originally Posted by Behemoth DT

<snip bullshit>If you will notice, old school doublers like the 203, is where you'll see your 8620 usually, and probably for a few different reasons.

Care to guess what those reasons might be?

They have been know to break them with only 4:1 Doubler/Tcase gearing, so using it in a planetary setup where there may be 50% - 100% more torque is asking for trouble.

So, how much is it? 50%-100% is quite the range, considering both are fixed ratio. Not that it matters, because you're wrong. A 2.72:1 ratio planetary will develop 35% more output torque than a 2.01:1 203 range box when given the same input torque. Not the 50%-100% figure that you pulled out of your ass.

DD schooled me on this for about an hour on the phone one evening, and I finally came to my senses.

I hope his math is better than yours...

4:1 doubler vs. 5.4:1 = 35% more gearing, and 4 speeds instead of 3

At least you got that one right...

4:1 doubler vs. 7.3:1 = 82.5% more gearing

I'm gonna go out on a limb here and assume you are talking about having a planetary range box in front of a 2.7:1 ratio chain drive case? Well, hot news flash: the torque on your intermediate shaft is still only 35% more than a 203 range box shaft. You seem to think the output torque from the transfer case is somehow transposed back upon the range box intermediate shaft, which demonstrates a clueless lack of knowledge of even basic mechanics.

stock low @ 2.7:1 vs 5.4:1 = 100% more gearing (OEM 8620 go boom)
stock low @ 2.7:1 vs 7.3:1 = 170% more gearing (OEM 8620 go boom)

Once again, you're a dumbass. That overall ratio is NOT being applied to the range box shaft. No matter what transfer case you use, a 2.72:1 planetary is always going to apply 2.72x the input torque to the intermediate shaft, which is still only 35% more than a 203 range box. Guess what else? The TOTAL torque multiplication you are quoting is being applied to the output shafts of the transfer case. Wanna guess what alloy stock transfer case shafts are made of? I will give you a hint: it starts with an 86 and ends with 20

----------------------------------SAE 4340----------------------SAE 8620

Modulus of elasticity---------------29,700 ksi --------------------29,700ksi
Tensile strength (annealed)--------108,000 psi--------------------77,800 psi
Yield strength (annealed)----------68500 psi---------------------55,900 psi
Hardness (annealed)---------------96 RB-------------------------80 RB
Tensile strength (normalized)-------195500 psi--------------------91,800 psi
Yield strength (normalized)---------125000 psi --------------------81,800 psi
Hardness (normalized)--------------112 RB ------------------------90 RB

Source:
http://aeonmaterials.com/alloys.aspx

Again, you're a dumbass. I never said 4340 wan't stronger than 8620. I said it wasn't the best material for this particular application. I did not say it wouldn't work (for a while anyway), just that it wasn't the best. In any case, when posting up relative strengths of materials, it may help to post them up in the proper heat treated conditions. You highlighted the strength for normalized materials, which shows you don't have a clue. Are you going to use normalized 4340? Good luck with that.

Like I said, pics will be a couple weeks away. I will post them in the vendor section.

Oh, I can hardly wait...

[MaxPF]

Originally Posted by Behemoth DT

----------------------------------SAE 4340--------SAE 8620-------SAE 4130

Modulus of elasticity---------------29,700 ksi ------29,700ksi-------29,700ksi
Tensile strength (annealed)--------108,000 psi------77,800 psi------81,300psi
Yield strength (annealed)----------68500 psi--------55,900 psi------52,300psi
Hardness (annealed)---------------96 RB------------80 RB----------82 RB
Tensile strength (normalized)-------195500 psi-------91,800 psi-----97,000psi
Yield strength (normalized)---------125000 psi ------81,800 psi------63,300psi
Hardness (normalized)--------------112 RB ----------90 RB----------93 RB

Source:
http://aeonmaterials.com/alloys.aspx

Fuck me! You really don't know shit about mettalurgy, do you? Nobody is going to use any of these alloys in the annealed or normalized condition. You are continuing to demonstrate your ignorance. Please stop while you have any shred of credibility remaining

EDIT: I see a HGTD coming soon....

[Behemoth DT]

So you want everyone to believe that there is no extra stress on the intermediate shaft when the Tcase is in low, opposed to high?

The output shafts are sharing the load.

Normalized values were given just for comparison sake.

The fact remains that 4340 is about twice as strong, and is the choice for many.

[MaxPF]

Originally Posted by Behemoth DT

So you want everyone to believe that there is no extra stress on the intermediate shaft when the Tcase is in low, opposed to high?

Lol, you just keep digging a deeper hole. In absolute terms the maximum stress on the intermediate shaft is the max input torque available x the gear reduction of the crawler box. Nothing the transfer case does can increase the torque beyond this amount. As a practical matter, low range in the transfer case generally REDUCES the stress on the intermediate shaft since the transfer case is now providing more of the required torque multiplication. That is why ORD warns their customers that any possibility of breaking their intermediate shaft is increased when the range box is in low and the t-case is in HIGH range.

Again, this shows your fundamental lack of knowledge in basic mechanical principles

The output shafts are sharing the load.

Not necessarily. Often times one axle is under much more load than the other. Even when the load is equal, a 205 with it's 1.96:1 low range will still put the same torque on each output as the torque applied via the intermediate shaft. If you understood mechanics and gearing you would know this.

Normalized values were given just for comparison sake.

Which doesn't mean shit since the normalized values show 8620 as having a higher yield strength than 4130, but once heat treated 4130 has a clearly higher yield point than heat treated 8620.

The fact remains that 4340 is about twice as strong, and is the choice for many.

Which would be great if ultimate strength was all that mattered. Unfortunately, there are other factors to consider which you don't even have a clue about. Again, the 4340 shafts will probably work fine for quite a long time, but it is certainly not the best alloy for the job. There are others besides 8620 that would be better suited and cheaper, but they don't have the bling factor that 4340 does. Why don't you use 300M? It isn't any better suited for the task than 4340, but it has even more bling factor.

[Behemoth DT]

All that is nice, but how about real world results?
How many 8620 doubler shafts have broken vs. 4340

And how many 4340 doubler shafts have had worn splines?

[MaxPF]

Originally Posted by Behemoth DT

All that is nice, but how about real world results?
How many 8620 doubler shafts have broken vs. 4340

And how many 4340 doubler shafts have had worn splines?

Worn splines aren't an issue, and broken 8620 doubler shafts are rare.

I'm bored with this thread, so let me explain the potential issue for the benefit of anyone who is considering spending their hard earned money on your range box. Take a look at the shafts in this pic:



See the ground surface on the end towards the camera? That surface rides on a pocket bearing in the input shaft. The needle bearings are made from straight chromium bearing steel and have a hardness of around 62-65 Rockwell C. Good engineering practice suggests that a shaft surface that is used as a bearing race be at least 58 Rockwell C. If the surface is too soft it is susceptible to brinnelling, false brinnelling, and fretting. You can eventually end up with a surface that looks like this:



Or worse, this:



Your 4340 shafts are going to be in the 40 Rockwell C hardness range. This is good for a combination of strength and toughness, but it's a piss poor surface to run a bearing on. The only reason you might get away with it is because the shaft has very little side load on it, but I still think it will slowly fret and wear from vibration. Luckily for you, the end user will probably never notice the bearing rumble deep inside his range box as this wear occurs.

203 intermediate shafts run roller bearings in the pocket in the end of the shaft. Unlike the pocket bearing in a planetary box, there is a LOT of side load on this bearing. Good thing you're not building these, because a 4340 shaft would last about as long as a fart in a hurricane.

The sad part is, it would take so little knowledge to actually do it right. 8620 is an excellent material, but if you need more strength 9310 would be just the ticket, and it would be cheaper than 4340 as well. If you're hung up on 4340 you might want to at least nitride it for wear resistance. This wouldn't work if the bearing was under much load, but it should work fine for preventing the inevitable wear you will get from a 64 rockwell bearing running on a 40 Rockwell shaft. Another option would be to machine the surface to a smaller OD and press on a hardened race made of 52100, O1, or even carburized 8620.

Finally, don't give me any shit about it being fine because others do it that way. I don't give a fuck. All is shows is that they either don't know any better or don't care. I have a stock 241 t-case mainshaft with false brinnelling in that exact location. This shaft was out of a 241 that never went into 4-lo and had functional pressurized lubrication, not the marginal splash lube yours will have. On top of that, every 241 shaft I have seen that has spent time in low range where lubrication is nearly nonexistant due to the low speeds shows abrasive wear on that bearing surface. Take a look again at the first pic in this post: the shaft on the right is a cut down used stocker, and it shows false brinnelling on the bearing surface. If this happens to a shaft with a hardness of 60-62 Rockwell, imagine what might happen to a shaft that is much softer.

I have provided a complete explanation of my perceived shortfalls in your "engineering". Now. assuming you don't delete this thread, I will let your potential customers figure out if they want to spend 800 bucks on a questionable adapter with a questionable shaft.

[DieselS10]

Originally Posted by BoondocK5

Plus, RCV will make you one of the shafts pictured for $185.00 plus shipping. and their customer service is unbeatable!

I'll have to remember this place, the intermediate shaft between my 241's handled the nearly stock 6.5TD fine, I'm a tad concerned about what i'm getting ready to put to it...

[MaxPF]

Originally Posted by DieselS10

I'll have to remember this place, the intermediate shaft between my 241's handled the nearly stock 6.5TD fine, I'm a tad concerned about what i'm getting ready to put to it...

No worries man. You will grenade a shaft, chain, or case on the 241 before you have a problem with the intermediate shaft

[DieselS10]

Originally Posted by MaxPF

No worries man. You will grenade a shaft, chain, or case on the 241 before you have a problem with the intermediate shaft

I figure your hitting it pretty close, but I already had them, so why not see what they'll take. I will be doing a severe de-tune on the LLY for when in low range, so maybe that will help keep them alive a little longer. This truck will spend 95% of it's time on the street too.

[MNtal]

Go away for the weekend and come back to this doozy of a thread...

[Mh4Runner]

I see the failure at the pilot surface in situations where there is a serious vibration from the driveshaft on stock t-cases a few times a year. I can appreciate the lesson in the different properties of the different alloys, but I wonder how much of it is on paper theories.

MAxPF, are there any documented cases of this deterioration of the pilot bearing surface from the from the use of 4340 in a doubler situation? I have seen it many times in stock T-cases where the output bearing is a fulcrum and the pilot bearing (and tailshaft bushing) must stabilize the output shaft. I have also seen a few resplined doubler shafts break.

Jake, how hard would it be (no pun intended) to do as MaxPF stated with the use of an 8620 sleeve pressed onto the pilot end to get the best of both worlds?

Despite his aggressive nature, I think he brings some potentially valid arguments to the table.

[Behemoth DT]

Originally Posted by Mh4Runner

I see the failure at the pilot surface in situations where there is a serious vibration from the driveshaft on stock t-cases a few times a year. I can appreciate the lesson in the different properties of the different alloys, but I wonder how much of it is on paper theories.

MAxPF, are there any documented cases of this deterioration of the pilot bearing surface from the from the use of 4340 in a doubler situation? I have seen it many times in stock T-cases where the output bearing is a fulcrum and the pilot bearing (and tailshaft bushing) must stabilize the output shaft. I have also seen a few resplined doubler shafts break.

Jake, how hard would it be (no pun intended) to do as MaxPF stated with the use of an 8620 sleeve pressed onto the pilot end to get the best of both worlds?

Despite his aggressive nature, I think he brings some potentially valid arguments to the table.

Actually, in a doubler this is a non-issue. There is zero side load.
In the BW cases the shaft's forward end first goes into a brass bushing, then on to the pilot bearings. In the BW doublers, the new shaft goes into the brass bushing only. It only supports the shaft when there is zero rotation. Once the rotation begins the shaft is instantly centered by the splines (this has been covered numerous times).
In the NP241 doubler the shaft "rests" on the pilot bearings at zero rotation. The moment any measure of rotation begins the shaft is forced to center. My shafts are undersized in this area 0.002". Once there is any measure of rotation, the shaft is forced to center, and will not make contact with the bearings.

[Mh4Runner]

Originally Posted by Behemoth DT

Actually, in a doubler this is a non-issue. There is zero side load.

This is only the case if everything is absolutely concentric, something I have been leery of since my first experience with a homebrew style doubler.

[enigma2y0u]

This is the most entertaining thread in the chevy section in a while. I just hope that the product is well built and reliable when released. Seems to me the major issue so far is the guy advertised a few weeks too early.

[Behemoth DT]

I do not disagree with you, although, think of all of the doublers that were assembled at home from kits that were machined in "bulk", and have survived for years.
Granted, it does all start with a good precision machined kit.

[Behemoth DT]

Originally Posted by enigma2y0u

This is the most entertaining thread in the chevy section in a while. I just hope that the product is well built and reliable when released. Seems to me the major issue so far is the guy advertised a few weeks too early.

Yea. No more will I give any kind of heads-up of up and comings. Hindsight is 20/20.

[MaxPF]

Originally Posted by Mh4Runner

MAxPF, are there any documented cases of this deterioration of the pilot bearing surface from the from the use of 4340 in a doubler situation? I have seen it many times in stock T-cases where the output bearing is a fulcrum and the pilot bearing (and tailshaft bushing) must stabilize the output shaft. I have also seen a few resplined doubler shafts break.

I have not seen any 4340 shafts, but I have seen the wear on stock 8620 shafts. These shafts have a surface hardness of ~60HRC vs 40HRC for a 4340 shaft. The wear I have seen was false brinnelling caused by the pilot vibrating on the relatively stationary bearing during normal 2wd operation. I have a shaft with this exact wear in my parts pile, and I have seen many others. It takes a lot of miles to do this to the hardened surface of the stock shaft. I doubt it will take much time for this to happen to the much softer 4340.

Originally Posted by Mh4Runner

This is only the case if everything is absolutely concentric, something I have been leery of since my first experience with a homebrew style doubler.

Even if it is perfectly concentric, the wear will occur just from normal vibration. As I said, it happens to stock shafts in 2wd (there is no side load in 2wd).

In the end, what I think doesn't matter. He is going to sell these, and his customers are going to do the failure testing for him.

[sweetk30]

Originally Posted by Behemoth DT

Yea. No more will I give any kind of heads-up of up and comings. Hindsight is 20/20.

just a idea

next time be prepared for the thread with correct pics and info. and when ready to post it click the preview post button and recheck your work. then you wont look like a dumb a$$ .

i dont care how good your work is now. but the way you have handled your self back pedaling in this thread i will never buy anything from you sorry. not the way to start as a new member let alone a vendor. and you cant even read the simple rules and post in the VENDOR SECTION

but this thread has been real fun

[Behemoth DT]

There is always side load when a chain is involved, 2WD or 4x4. There is no internal mechanism that tightens the chain for 4x4, and loosens it for 2WD, it is always tight.

[oldrivers]

how much side load is there on a pilot bearing anyways , i mean the whole assembly is connected by gear teeth , mainshaft to planetary , to imput gear and then the side load is carried by the larger imput bearing correct ? i noticed they canceled out the little roller bearings on the mainshaft chain sprocket and went to a machine surface . maybe they could do that to the piloit bearing aswell. like a clutch went to a bronze pilot bearing instead of the roller bearings .

[MaxPF]

Heck, if you're so sure there is going to be no load whatsoever on the pilot, why not just delete it entirely

[Behemoth DT]

Originally Posted by MaxPF

Heck, if you're so sure there is going to be no load whatsoever on the pilot, why not just delete it entirely

Originally Posted by Behemoth DT

In the BW cases the shaft's forward end first goes into a brass bushing, then on to the pilot bearings. In the BW doublers, the new shaft goes into the brass bushing only.

.