Duramax Diesels Forum Truck of the Week
  #46  
Old 12-08-2018, 08:26 AM
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I still have that truck with the transfer case in it, I have about 40-50k more miles on it and still rolling around with a 1k ft lbs tune and no issues other than what was mentioned in the beginning to date.

I recently contacted a company and having them make a special output shaft for the Allison (32 splines, high quality steel, heat treated etc.) to try a 08-09 H2 transfer case(BW4484). It has 4-high-open, 4 high-lock, 4 low for positions. Then having them make an input shaft for the Silverado SS case (NP149) that's 32 splines, that one is a viscous clutch. Just to try them out, as you can tell I enjoy AWD vehicles and these projects. I will also update those like my current case to handle a bit more power.

This time next year I intend on building a single-cab-short-bed duramax(LBZ) - Boxed-frame, slightly lowered, big sway-bars, poly bushings, built front-end; basically make it one the of the best handling duramax's possible.
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  #47  
Old 12-09-2018, 07:06 AM
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Quote:
Originally Posted by chrisuns View Post
I still have that truck with the transfer case in it, I have about 40-50k more miles on it and still rolling around with a 1k ft lbs tune and no issues other than what was mentioned in the beginning to date.

I recently contacted a company and having them make a special output shaft for the Allison (32 splines, high quality steel, heat treated etc.) to try a 08-09 H2 transfer case(BW4484). It has 4-high-open, 4 high-lock, 4 low for positions. Then having them make an input shaft for the Silverado SS case (NP149) that's 32 splines, that one is a viscous clutch. Just to try them out, as you can tell I enjoy AWD vehicles and these projects. I will also update those like my current case to handle a bit more power.

This time next year I intend on building a single-cab-short-bed duramax(LBZ) - Boxed-frame, slightly lowered, big sway-bars, poly bushings, built front-end; basically make it one the of the best handling duramax's possible.
The short bed boxed frame you mentioned, are you using a 2500hd shortened too short bed and box it or using a 1500 frame boxed up? I've always thought how cool it would be to have an AWD single cab short bed Duramax meant to handle the track or windy roads where I live. The suspension, would it be coil overs or airbags or sticking with stock torsion bars?
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  #48  
Old 12-09-2018, 08:14 AM
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Originally Posted by Ridin'GMC View Post
The short bed boxed frame you mentioned, are you using a 2500hd shortened too short bed and box it or using a 1500 frame boxed up? I've always thought how cool it would be to have an AWD single cab short bed Duramax meant to handle the track or windy roads where I live. The suspension, would it be coil overs or airbags or sticking with stock torsion bars?
I'll for sure be sticking with a 2500 frame and shortening that; I may even try to put a 2011+ frame on it to getting around from boxing the 01-10s. Those are the two options that are on my mind at least - I still have a bit of research to do in that department.

The front suspension I'll more than likely leave torsion; the rear: a 5 link air setup has been on my mind - maybe a Keldermans, or even custom (pending I decide to buy a CNC plasma table and CNC machine I've been looking at). Although, specifics like that will be further down the road, since this will likely be one of the vehicles I keep for the rest of my life, as a toy.

It's mostly in the planning stages/slowly looking around for the right truck when time allows at this point in time.
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  #49  
Old 12-16-2018, 05:15 PM
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Quote:
Originally Posted by chrisuns View Post
I still have that truck with the transfer case in it, I have about 40-50k more miles on it and still rolling around with a 1k ft lbs tune and no issues other than what was mentioned in the beginning to date.

I recently contacted a company and having them make a special output shaft for the Allison (32 splines, high quality steel, heat treated etc.) to try a 08-09 H2 transfer case(BW4484). It has 4-high-open, 4 high-lock, 4 low for positions. Then having them make an input shaft for the Silverado SS case (NP149) that's 32 splines, that one is a viscous clutch. Just to try them out, as you can tell I enjoy AWD vehicles and these projects. I will also update those like my current case to handle a bit more power.

This time next year I intend on building a single-cab-short-bed duramax(LBZ) - Boxed-frame, slightly lowered, big sway-bars, poly bushings, built front-end; basically make it one the of the best handling duramax's possible.
I have a project that I want to use with the np149 behind a 6l90, not as much power as your running though.
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  #50  
Old 11-07-2019, 09:44 AM
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I've now done this basic conversion on both of my rigs. Did the 2003 LB7 Suburban a year or so back. Ended up paying a transmission shop to do the mechanical side of things. The electrical was easy on the Suburban, because it originally had the NP246, so basically just plugged the original TCSCM and harness back in.

I liked that so much that when I (thought I) killed the 263XHD in my GMC, I used it as an excuse to do the same thing. This time required a good bit more wiring, since the body harness didn't have the necessary wiring. My brother and I went to a junkyard and pulled the body harness apart on a Suburban, and took the complete AWD wiring out of it.

Not wanting to completely rip my truck's dash apart, I loomed the additional wires for the AWD case (front driveshaft speed twisted pair, rear driveshaft speed twisted pair, motor brake return) into their own harness and poked it through the firewall next to all my other aftermarket crap. This ended up being a much more direct route than the factory routing, so I had a bunch of extra length. Not wanting to cut & crimp new pins on (long-term plan is to loom this into the stock harness next time the dash comes out), I just made a big U going up towards the top of the dash then back down to the TCSCM, and added the new wires to the factory connectors. I avoided looping the harness to prevent cross-talk. Under hood, everything uses the stock AWD connectors, so the transfer case extension harness is all original and just plugs in.

This seems to have worked nicely, as the AWD system works perfectly! Both the transmission shop and I are a little worried about the smaller output shaft on the 246 vs the 263XHD. I plan to take it to the track next year and beat on it, so we shall see how it goes.
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  #51  
Old 11-08-2019, 07:24 AM
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Guys, one thing that hasnt been mentioned (or maybe Im dense) is, "Just how did you both actually connect the 246 to the Allison and driveshafts in the first place?" b/c the spline counts and trans output shafts are different?

Did you pretty much have to swap all the 261/263 internals over in the end?

Also, just what was involved with the harnesses? More sekrut skwirl stuff? That was another point that was never fleshed out.
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  #52  
Old 11-08-2019, 09:55 AM
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No secret squirrel, but you're right, this thread has been short on DIY.

The mechanical side of things is not my cup of tea (which is why I paid Ultimate Transmission to do it), but let me see if I remember what they said they did. Take this with a grain of salt, as I don't remember things I don't care about super clearly. The main shaft on the transfer case is the 2 pieces. You take the front piece out of a 263XHD and that fits the Allison just fine. The main shaft is from the 246 to fit the clutch pack. You can make the large chain out of the 263XHD fit on the 246 shaft. There is some machining work, but I can't remember if it was on the shafts to get the 2 to connect together, or on the front 246 case half to take the larger input shaft. The rear case halves are basically the same. The 263XHD back has the blanks for the speed sensors. You can just drill those out, or use the 246 back half. The 246 main shaft is smaller, so you use a larger bearing and seal on the output. I am using the smaller yolk to attach the driveshaft on both of my rigs. The trans shop thinks that is the current weak link at my power level (~700 WHP), but we will see.

The electrical side is my jam, though. And honestly, it isn't that hard if you add new wires separately, instead of adding them into the stock harness. Even then, the hard part is getting the dash pulled apart and back together.

There are only 5 wires that need added (mentioned in my previous post). I've attached the factory wiring for the 263 and the 246 so you can see where they all go. Once you add the wires, you are good to go to plug in a 246 transfer case harness, and it just works.

The 246 pushbutton module uses a different connector, but the pins are all the same. I just de-pin the 263 pushbutton connector, then put those pins and the 1 new wire into the 246 connector. Might as well take the 246 pushbutton apart and put new bulbs in at this stage. Then it just plugs in and clips into the dash.

If you have any questions about the electrical, I can help.
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