drdave81

Not sure if anyone would really even be interested in this. Based on searching, there aren't a whole lot of people who have done it, but I thought I'd throw this out there anyway. I'll say now, I'm pretty horrible about taking pics during my work. I get focused on it and usually forget to get anything good.

Parts Needed:
NP149 AWD transfer case from 00-02 Yukon Denali or 02 Escalade. You can also get it from an AWD Silverado, but those probably are less common to come by. (RPO code is NP3)
Front Driveshaft from any 00-06 Denali or 02-06 Escalade
Cubby/pocket to replace the 4x4 switch from donor vehicle
A piece of PVC with an OD of about 3/4", cut down to 3/4" length
New gasket between the rear of the trans and the transfer case (Fel Pro 72770)
2.5qts of Auto Trak II transfer case fluid

Procedure:
You'll need to remove the rear driveshaft and the front driveshaft from your current transfer case. Then drain and remove the transfer case. Then install the new NP149 transfer case with the new gasket. I also installed a new output shaft seal as the old one looked a bit rough. Don't forget to plug the output speed sensor, the other connectors will just hang out, I ziptied them out of the way. Now, when you install the rear driveshaft, you'll notice it sticks out a bit further than it did before. This is because the NP149 is 1 inch shorter than the NP246 that came out of my truck. Not a huge deal as there is still plenty of yoke to engage the transfer case. I do plan to lower this truck so it will eventually make up for this. The case being 1 inch shorter on the front half of the case is also the reason you have to have the front driveshaft from the donor vehicle, as the 246 front driveshaft will not fit......... trust me, I tried. It shifts the whole front of the transfer case forward.



OK, the transfer case and driveshafts are installed, good to go....... no not yet. Now is where you need to permanently lock the front axle. This has to be done due to the design of the transfer case, and it's viscous coupler internally. If all 4 wheels do not constantly have power, you will burn up the coupler. You could also get the front axle from the donor vehicle, but my truck has 3.42 and all the Denalis and Escalades are 3.73. I have dropped enough money on a 6.0L swap and trans upgrades, so I wanted to keep this cost down for now. This is easy enough to accomplish though.
1. Key on, shift to 4hi. Shut the key off and disconnect the actuator connector. It will stay engaged. Don't ever plug it back in or it will pop back out once you key on again..... after it sees no signal from the old transfer case anymore.
2. The first option did work, I drove around for 15 miles like that and it stayed, but I had this (possibly irrational) fear that it may eventually move, so I opted for a piece of PVC pipe in place of it. The actuator travel distance is right about 3/4", so that's how long the piece needs to be cut. It's also about that diameter. I plugged the actuator back in, it retracted and unlocked the axle. I removed the actuator and glued the PVC to the end of it. Once I threaded it back in, it pushed the shift fork and locked the axle again. This will be permanent. (I wish I'd grabbed a pic of this)
Next I jacked up the vehicle to get all 4 wheels off the ground. I started it up and pulled it into drive, all 4 wheels are moving at the same time. This is also not recommended as it will damage the coupler, but as a test verification, it was ok. I put it back on the ground and out for a test drive. You will have a "Service 4WD" cluster message at this point. The final step is to remove the bezel from around the cluster. Remove the 4x4 switch and the module behind it, or at least disconnect everything. Install the pocket from the AWD donor vehicle and you are the coolest guy on the block now.

A note: I know the 03-06 Denalis and Escalades are also AWD. Those are a Borg Warner T case that is an open diff and relies on an ABS input for AWD. The NP149 is a strictly mechanical case, so it makes this the easiest way to swap. Are there other options, probably. But K.I.S.S.

I welcome any feedback anyone may have, and maybe this will help someone else some day. If not, well, I didn't have to pay attention to a work meeting for the bit of time I wrote this up.