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Old April 4th, 2012, 11:20 PM   #1
cerial
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Default Fllat flange to flat flange question

I am putting 2 overdrive boxes behind my transfer case in a truck.
The 2 overdrive boxes have flat flanges at both ends and will mount like a divorced transfer case.

What I am wondering is if I could use a single u joint eliminating the center yoke?
Or if this a horrible idea which will lead to bearing and seal issues?


Could I get away with this?
|{o}|

Or would I need to go with the center yoke which is considerably longer?
|{o}|{o}|

When you compare the two you can easily see why I want to do this if it is possible.

TC{o}|OD|{o}|OD|{o}|{o}Driveshaft{o}Diff

TC{o}|{o}|OD|{o}|{o}|OD|{o}|{o}Driveshaft{o}Diff
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Old April 4th, 2012, 11:30 PM   #2
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what is the wheel base? why put the brownie boxes behind the tcase?
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Old April 4th, 2012, 11:31 PM   #3
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Couldn't the gearing of one overdrive unit be adjusted to eliminate the mechanical advantage of having two units?

I'm just trying to see why you feel you need two units?

That, and as asked, why you wanted them post transfer case?
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Old April 5th, 2012, 12:02 AM   #4
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he over thinks shit and isnt actually going to do it. this doesnt make any sense to do this at all. what are you trying to actually build?
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Old April 5th, 2012, 12:39 AM   #5
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A 52mpg plastic jeep with a rusted out Nickle plated frame.
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Old April 5th, 2012, 05:57 PM   #6
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Quote:
Originally Posted by deerebowtie View Post
what is the wheel base? why put the brownie boxes behind the tcase?
Quote:
Originally Posted by kargod View Post
Couldn't the gearing of one overdrive unit be adjusted to eliminate the mechanical advantage of having two units?

I'm just trying to see why you feel you need two units?

That, and as asked, why you wanted them post transfer case?
I am using the 2 3 speed(2.0,1.0,.72)brownies to get a .72 and .51 ratio. They will also let me split the gears depending on the load.

I was going to use one (2.0,1.3, 1.0 box) and run a .5/1 gear reduction before it. The fact is the Under, under, direct box is a lot harder to find and would be harder to get parts for if I needed to replace it. The cost of a .5/1 box is more then a second brownie and if broke I would be screwed.
Finding the more popular under direct over (2.0, 1.0, .72)brownie is a lot easier. These boxes are more similar to 2 speed rear end then a transmission having 2 pinion yokes. Changing gears is complicated and not worth the hassle. I am going the simpler route that I know will work.


This is for a tow rig I do not need the low ratio before the transfer case. The truck has a 65/1 craw now. That is enough for something where the 4wd will only be used in light muddy conditions. I don't actually need the low ratio at all it is just easier to find the boxes with the under,direct, over.

Quote:
Originally Posted by boggin-machine View Post
he over thinks shit and isnt actually going to do it. this doesnt make any sense to do this at all. what are you trying to actually build?
I am doing it and it does make sense. It gives me a very reliable .72 and .52 overdrive while letting me keep the low gearing in the rear end for towing. Mounting 2 brownies is the toughest, easiest to replace, and most simplistic drive train that will give me the ratios I want without replacing the entire power train.
I have done the math a few hundred times. It will pull 13k(conservative number) up a 6% grade maintaining 55 mph easily. I know that is not impressive by today's standards. But, it is better then most and will work for this rig. The impressive numbers are below 52 mph where most of the work is done.
The .52 ratio is only used above 55 to reduce wear. I plan on maintaining a towing speed between 55 and 65 in this. I don't see myself driving faster then 70 empty to save both wear and fuel. I can drive 70 without using the second overdrive If need be. But the engine is out of the power range going that speed increasing wear and reducing mileage. Using the second overdrive keeps the engine in the power range from 52-72 mph.

I am simply seeking advise if I can eliminate the center yokes in a effort to lengthen the rear drive shaft. I do have the wheel base to make this work either way. If I can eliminate the center yokes it means less parts to replace and the less chance of vibration.

With everything in line I believe eliminating the center yokes is possible. Maybe I am missing something though. Which is why I am looking for feedback from people that have more experience in(old school) dual divorced transfer case setups and such.
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Old April 5th, 2012, 07:34 PM   #7
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why not run a 5 speed overdrive and one single aux box. i have plans to build a splitter for behind my Nv4500. if i ran a .72 overdrive behind my .73 in the main trans that would leave me with a .52 overdrive.
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Old April 5th, 2012, 09:00 PM   #8
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How are you mounting the engine, trans, t-case, and brownie box?
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Old April 5th, 2012, 09:07 PM   #9
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why not run a ZF6? OR get a new truck.
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Old April 5th, 2012, 09:20 PM   #10
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Quote:
Originally Posted by Kodiak450r View Post
why not run a 5 speed overdrive and one single aux box. i have plans to build a splitter for behind my Nv4500. if i ran a .72 overdrive behind my .73 in the main trans that would leave me with a .52 overdrive.
Thats a good setup. You should be able to run taller gears in the rear for more pulling power.

I am trying to create a "period correct" drive train. I like the engine and trans in this. Currently I am having the transfer case rebuilt. The engine and transmission have already been rebuilt. I have one brownie that should be arriving in a few days that has been fully rebuilt. I have sources on a second I am waiting back on a rebuilt quote while keeping a eye out.

The current engine and 420 transmission can be rebuilt for less then 2k in parts and and a week of my time once they get some miles on them.
I would have that much in a adapter and worn 4500 easily. It would be cheaper to buy a engine mated to a 4500 and so on and such. You can see how that is a slippery slope.
This is a very simplistic old school drive train and I want to keep it that way. I am making a few upgrades for safety but I am not trying to mess with the cheap and reliable drive train I have. I just want to go a bit faster in it without causing excessive wear.



Someone must have done or seen someone mount dual divorced cases in a old school rig wanting to eliminate the 4 or so inches a center yoke would add. It does not make sense now because of all the adapters and kits out. But back in like the early 90's or so it would seem like more people would have seen what I am talking about.
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Old April 5th, 2012, 10:10 PM   #11
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Been searching on pirate and other sites for the last few hours looking to a answer to this.

Seems this question has been asked quite a bit and the safe bet is to go with the center yoke. There is a lot of evidence that it is possible and some people get away with doing it. I don't plan on flexing this thing but who knows I may hit a deep pot hole or rail road tracks which could flex and break the joint. The risk of breaking outweighs the 10-12" I would see in additional drive shaft length.

Playing the safe card and using the center yoke. I will just run a Multiple Double Cardan drive shaft to eliminate vibration.
Thanks for all the help.
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Old April 5th, 2012, 10:47 PM   #12
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Quote:
Originally Posted by Diesel Dan View Post
why not run a ZF6? OR get a new truck.
zf6 ratios
1st 5.79
2nd 3.30
3rd 2.10
4th 1.31
5th 1.00
6th 0.72
rev 5.23

My 6 speed setup ratios
1st 6.68
2nd 3.10
3rd 1.69
4th 1.00
5th 0.72
6th 0.52
rev 8.25

If I wanted to I could leave the 1st brownie in high which would only require 5 shifts.

1st 4.80
2nd 2.23
3rd 1.21
4th 0.72
5th 0.52
6th -
rev 5.94

If I put them both in high I would only have 4 shifts

1st 3.46
2nd 1.60
3rd 0.87
4th 0.52
5th -
6th -
rev 4.27


It is a set it up as your needs change setup. I don't plan on doing any hands off the wheel shifting though so I will probably stick with picking a range and running it.

Last edited by cerial; April 5th, 2012 at 10:54 PM. Reason: .point
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Old June 17th, 2012, 02:43 PM   #13
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you cant run 1 u joint on a shaft. must be 2
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