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T-case & Doubler comparison thread...

Stephen said:
And now for some general underdrive system tech.

Any time you underdrive a transfer case you have to consider the torque capacity of the intermediate shaft and transfer case input. It's intuitively obvious that anytime you double or triple the input torque on the input of a transfer case you stand a chance of breaking that input and this torque increase is exactly what you do with an underdrive.
So what we look at with a 205 specifically is that you have two 32 spline output shafts that are good for about 4000 ft-lb of torque (to use a round number) each. If the 205 is in high range you can put 8000 ft-lb into the 205 to reach the breaking strength of both outputs. Obviously this 8000 ft-lb is way over the strength of a 32 spline input since a 32 spline input is only good for the same 4000 ft-lb of torque. This is why it's bad to run most underdrive systems with the front box in low and the 205 in high

Let's mix this up and put the 205 in low range. Now we have a 2:1 torque multiplication between input and output so the 8000ft-lb that the output shafts can support can be generated by only 4000 ft-lb from the input.
input at 4Kft# * 2:1 gear reduction = 8Kft# split between the two outputs.

Fortunately the good old 203 doubler system has 2:1 gear ratios in both boxes so there is no reason to ever run the 203 in low and the 205 in high. This makes it easy to run it right all the time and as such it's a really tough system.

The problem comes in when we start using planets that are a 2.72 reduction. Now that front gear reduction is useful to use by itself and it's also a deeper reduction so it's harder on the intermediate shaft....
Click to expand...


Stephan, please don't take this as a dig on the Magnum box, because it's not. I love what ya'll did with it.

Kind of long, but, a real question at the end.

When I built my 241/205, I built it because I wanted lower gearing and in no way could afford for the $2-3-4K for one of those uber cool boxes made by the big boys.
So, I resorted to what I always do, build what I can, the best I can.
I also had "heard" that there were issues with strength at the Intermediate shafts, when made in this configuration. It made sense mathematically.
To counter this, I went with the strongest shaft I could find. Not what I could afford, what I could find.
RCV Performance's "lifetime guarantee against breakage, no questions asked", spoke volumes to me.
They have a reputation for building axle shafts that just plain don't break.
I'm no metallurgist, just a mechanic who has bent his and someone else's fair share of wrenches.
I honestly cannot find anyone, anywhere, who has broken an intermediate shaft, in this configuration, not saying it couldn't happen, I just couldn't find any record of it. Even those cut down 241 main shafts seem to hold up, which surprised the hell out of me.
I completely understand the mathematics of the torque input vs output vs input.
I just don't see myself ever breaking that intermediate shaft in my 241/205 doubler. I don't do big blocks, nor do I get a case of the stupids while on the skinny pedal.
In fact the only wheeling experience I have is from no BS, 30 years ago as a kid when I enjoyed flogging the living daylights out of stock 76 blazer in corner canyon here in SLC, UT.
So, time will tell.

Now the question,
Just so no one wastes their hard earned $$$$ and time on a doubler that may break.
Can anyone honestly see the intermediate shaft, (the Lifetime Guarantee shaft) from RCV Performance, breaking, during what even the most inexperienced wheeler (probably me) will do to it in Moab, on even my worst day of AHAADD driving?

My answer, is probably not. I might explode the case, but I don't think I'll hurt that shaft.

Now, if I ever build a balls out, bomb proof rally rig, then yes, I want that Magnum box, it's just beastly strong and too freaking cool!
 
They did revise the the atlas 4 and it's a little longer now. The shifter configuration is a good way to tell which is which since that changed with the generations.
 
Matt if you run your 241 in low with your 205 in high alot, you probably won't break it right away but it will lead to enough fatigue that it will more than likely cause failure. It is generally accepted in almost any doubler ( there are tons out there) you should not run the range box in low with the transfer case in high. Although in some discussions I have had the concern is not with the male splines on the shaft but the female end of the conglomeration, being that the shaft will not break but will strip the splines on the input of the second case. The shaft is not necessarily the weak spot its where that shaft rides. Those splines were never designed for that kind of torque load.

Thats my take on it and it makes sense to me. Even more sense after I see what kind of shaft is being used on the Magnum ( sorry guys that name makes me giggle :D)

Stephen or Chris can correct me if I am totally off base
 
BoondocK5 said:
Stephan, please don't take this as a dig on the Magnum box, because it's not. I love what ya'll did with it.

Kind of long, but, a real question at the end.

When I built my 241/205, I built it because I wanted lower gearing and in no way could afford for the $2-3-4K for one of those uber cool boxes made by the big boys.
So, I resorted to what I always do, build what I can, the best I can.
I also had "heard" that there were issues with strength at the Intermediate shafts, when made in this configuration. It made sense mathematically.
To counter this, I went with the strongest shaft I could find. Not what I could afford, what I could find.
RCV Performance's "lifetime guarantee against breakage, no questions asked", spoke volumes to me.
They have a reputation for building axle shafts that just plain don't break.
I'm no metallurgist, just a mechanic who has bent his and someone else's fair share of wrenches.
I honestly cannot find anyone, anywhere, who has broken an intermediate shaft, in this configuration, not saying it couldn't happen, I just couldn't find any record of it. Even those cut down 241 main shafts seem to hold up, which surprised the hell out of me.
I completely understand the mathematics of the torque input vs output vs input.
I just don't see myself ever breaking that intermediate shaft in my 241/205 doubler. I don't do big blocks, nor do I get a case of the stupids while on the skinny pedal.
In fact the only wheeling experience I have is from no BS, 30 years ago as a kid when I enjoyed flogging the living daylights out of stock 76 blazer in corner canyon here in SLC, UT.
So, time will tell.

Now the question,
Just so no one wastes their hard earned $$$$ and time on a doubler that may break.
Can anyone honestly see the intermediate shaft, (the Lifetime Guarantee shaft) from RCV Performance, breaking, during what even the most inexperienced wheeler (probably me) will do to it in Moab, on even my worst day of AHAADD driving?

My answer, is probably not. I might explode the case, but I don't think I'll hurt that shaft.

Now, if I ever build a balls out, bomb proof rally rig, then yes, I want that Magnum box, it's just beastly strong and too freaking cool!
Click to expand...

People break them, we've sold a couple shafts to people who broke theirs (who knows who made their shaft) and I know there have been companies that built 300M outputs for the Klune etc.

Having said that, I haven't broken mine yet and we have a 241 chop box kit so it's not like we don't appreciate that angle. That intermediate shaft is the weak link in the system but it's not made of glass.

We're catering to both: a cheaper, more do-it-yourself option that gets you the gearing in a strong package, and an end-all option that is the final word in strength with all new parts. We leave that choice up to you but either way we do it right and the gearing rocks!
 
Stephen said:
Fortunately the good old 203 doubler system has 2:1 gear ratios in both boxes so there is no reason to ever run the 203 in low and the 205 in high. This makes it easy to run it right all the time and as such it's a really tough system.
Click to expand...

Except for that there is only one shifter for the NP203 and it shifts much easier than an NP205.

Martin
 
38377k5 said:
People break them, we've sold a couple shafts to people who broke theirs (who knows who made their shaft) and I know there have been companies that built 300M outputs for the Klune etc.

Having said that, I haven't broken mine yet and we have a 241 chop box kit so it's not like we don't appreciate that angle. That intermediate shaft is the weak link in the system but it's not made of glass.

We're catering to both: a cheaper, more do-it-yourself option that gets you the gearing in a strong package, and an end-all option that is the final word in strength with all new parts. We leave that choice up to you but either way we do it right and the gearing rocks!
Click to expand...

Thanks for being understanding Chris.
I really appreciate being able to discuss this without everyone getting all butt hurt.
You guys at ORD are true Professionals!:bow::bow:

So, uh, what is the total length on that "beastly shaft" for the Magnum box? AND, how much for just the shaft?

See where I'm going?:whistle:
 
Stephen said:
It's not built to be cheap or compete with any other underdrive, it's built to be the strongest most versatile transfer case system there is and the price really isn't out of line for what it does. In fact we might be selling it cheap to start with. Complete Magnum box WITH input conversion for the NP205 is $1990. It comes with free TCT too.
Click to expand...

That's not too bad. I'm gonna have to save a bit more to get it tho. What's TCT?
 
miniwally said:
Really?

There are a couple of guys running atlas 4 speeds in the desert/koh that run the 2:1 all the time with like 4:10 axle gears and 4 speed autos. then in the rocks they shift the planetaries in.

Meaning they run the planetaries in hi for desert racing and they have held up for several years now. One of them completed V2R in 09' which was a 1,000 miles.

In all honesty Micheal for what you do and like to do with your blazer a 241 SYE is good. A 205 would suck a bit more gas and shorten your range and I know that you like to drive your truck to and from the trails and also do longer exploring trips.

A happy wife is a happy life. Just keep saying that over and over and over:haha:
Click to expand...

Yes, based on available info 2 years ago, just when AA pulled the 4-speed for 'redesign'. I 'found' other uses for the money, though...:D

While I would like to know what 5.3:1 feels like, I'm fully aware that I don't need it - actually, what I'm going to need is a trailer to carry more gas for where I want to go next :D

Now back to your regularly scheduled programming.
 
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