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The elusive NP205 6x6 transfer case

highway101

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Joined
Sep 27, 2023
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6930
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I have searched the Internet and have not found a suitable way to go 6x6 with an NP205 transfer case. There are some shafts that go through on the lower side but tie the front to the rear at all times.

The problem with the NP205 is the way the input comes into the front gear rather than the shaft like the NP200 and 201 do. The problem with using the 200 or 201 is that the input gear in high range turns twice the speed of the shaft and relies on splash to oil the bearings. In high speed conditions (anything over 45 mph) they have a tendency to get hot.

I have a plan to address all these problems and create a 6x6 205 transfer case that has high and low range and is able to be used in 2,4or6 wheel drive. This will also include the 203 range box and the 203 differential section. I will post more later on this.
 
You need a np202 guts and a late model np205 swap the guts (not totally sure this would work, but mostly good idea) into a np205.

This would give two drive lines out the rear and one out the front.
 
wvracer821 said:
this has a 6x6 option
herotransfercase.com

Hero Transfer Case - 2Speed

The strongest, award winning reduction box on the market.
herotransfercase.com herotransfercase.com
Click to expand...
Screenshot_20230930_083514_Chrome.jpg
:eek:
 
shortbus4x4 said:
I know that's what he did for version 1.0 as I sent him the guts from a donor M715 NP200 of mine. I thought he had to rework it and did something else eventually.
Click to expand...

I messaged him on the old site when I was looking into this same concept. He said he had to do some shimming to get everything to line up correctly due to the difference in gear width. He didn’t mention a 2.0

I was trying to make a dual offset to the drivers side and retain front dig. It’s possible but would require a lot of custom machined parts.

I’m looking forward to seeing how he did it.

Hero cases can be dual offset but they require a 3 speed case and become a two speed case when done. They’re also $5k
 
What are you building?

Plenty of axles available off tandem drive trucks if weight isn't much of an issue.
 
I have most of the parts in the shop now. Next week going to get a couple pieces from Jantz Engineering to adapt to the 203 shaft. Working on customer projects for the next couple of weeks so don't have much time to invest in this.
 
I believe there were some successful home brew 6x6 using a divorced 205 behind regular t case, turned around, in 4hi, so the rear output is now the front input driven off the trucks rear output, then the input and the front output run drivelines to the rear diffs

The trucks primary tcase handles hi and low and powers the front diff
 
highway101 said:
I have searched the Internet and have not found a suitable way to go 6x6 with an NP205 transfer case. There are some shafts that go through on the lower side but tie the front to the rear at all times.

The problem with the NP205 is the way the input comes into the front gear rather than the shaft like the NP200 and 201 do. The problem with using the 200 or 201 is that the input gear in high range turns twice the speed of the shaft and relies on splash to oil the bearings. In high speed conditions (anything over 45 mph) they have a tendency to get hot.

I have a plan to address all these problems and create a 6x6 205 transfer case that has high and low range and is able to be used in 2,4or6 wheel drive. This will also include the 203 range box and the 203 differential section. I will post more later on this.
Click to expand...
This isn't the solution you probably want. But you could use a front axle in the rear with locking hubs. Saves gas, rear steer ready, and you get to turn 4 hubs instead of two 😂
 
I have been back working on this and have settled on how to do it today. All of the designs that I have worked out still operate the transfer case like an NP200. I don't like this design because the front top gear turns twice as fast as the input shaft. The NP202 transfer case has a split counter shaft which eliminated the high speed gear problem in the NP200 and NP201 with the knock gear.

The other problem is that with the NP200 design is the lack of a PTO which in the NP205 runs off of the input gear. The NP201 and NP202 address the lack of PTO by adding a gear in front of the main case and a 10 bolt PTO.

Now how to split the gear in an NP205?
After looking at how the NP202 was built I thought of using roller bearings in place of the tapered roller bearings on the shaft with shimmed end play. Since I want to use an NP203 gear case for a doubler I have a lot of parts that won't be used out of that.

The fix is to machine the main shaft out of NP203. The end with the splines will be turned down to the size of the NP205 idler shaft and threaded on the end. This will create a step that will seat against the front of the case on the inside where the thrust pad is. On the back side where the shaft steps up it will be machined to the size of the back part of the NP205 pin. In the NP203 is a thrust washer with a small pin that stops the rotation this will create the rear thrust pad that is not in the NP205 case.

Riding on the shaft will be the standard NP203 roller bearings and spacers in the sprocket shaft sleeve. The sprocket shaft sleeve will have the bevel gear turned off and the area just ahead of it made smooth and of the right diameter to fit the inside of the NP205 back gear. It will then have flats in the surface like the counter shaft of the NP202 or the lower shaft of the NP205. The sprocket gears will be turned down to fit inside the front counter gear and for prototype purposes be welded into the gear. The other one will have shift collar teeth cut into it.

All this will allow the NP205 to have a normal input gear and also be able to have a PTO output. I have an NP201 that I am taking the park brake off of for the NP205 currently in my 70 Dodge W200. I have to get the snap ring and bearing recesses machined into it so I can bolt it on. When adapting this to the NP205 you want to use one off of the NP201 or NP202 because they are designed to clear the PTO shaft and the NP200 brake isn't.
 
The class 8 trucks use or used what the switch on the dash called interaxle differential, I believe this air switch locked the driveline of both axles together or let one freewheel.

Having a look at those differential sets could give ideas to make it work with one ton differentials.
 
PAE said:
The class 8 trucks use or used what the switch on the dash called interaxle differential, I believe this air switch locked the driveline of both axles together or let one freewheel.

Having a look at those differential sets could give ideas to make it work with one ton differentials.
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Yeah... I don't fucking think so:shaking:.
1717955000503.png
 
M92PV4U said:
Are any of them going to be easily adapted to a light truck axle?
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No. Because if you're hauling enough weight in a light truck to require 3 axles it's cheaper, quicker and easier to go with a medium/heavy duty truck that already was engineered, designed and built with three axles.:homer:

The army in WWII figured this out with the Dodge WC62/63 6X6.
 
M92PV4U said:
Are any of them going to be easily adapted to a light truck axle?
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Not my fucking problem.

I watch mdt street tards and try to explain to them every god damn day why the gear ratio swap they want doesnt exist, the problems with trying to swap a dozen other axles in place, the convo ends, then they repost the question again in a new post.
 
shortbus4x4 said:
The army in WWII figured this out with the Dodge WC62/63 6X6.
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The Soviets really liked the tri-axles that were basically a clone of a Ford truck with Timken tandem rear axles stuffed under it (which were a flop in the US).
 
arse_sidewards said:
inb4 UB cups and custom shafts. :flipoff2:
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Our rig uses a transfer case without one front imput and two rear outputs each one can be ran simultaneously, independently or placed in neutral. It is 3 row 80 chain driven and the case is all "sheet metal" the "hubs" are cast but I'm sure could be CNCd these days. If I was making a three axle truck I would copy or build something similar.
EDIT: output power is controlled by external twin disc clutches.
 
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M92PV4U said:
Our rig uses a transfer case without one front imput and two rear outputs each one can be ran simultaneously, independently or placed in neutral. It is 3 row 80 chain driven and the case is all "sheet metal" the "hubs" are cast but I'm sure could be CNCd these days. If I was making a three axle truck I would copy or build something similar.
Click to expand...
That's awesome. Pics?
 
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