Hello everyone. This is my first post here, so bear with me. Couple weeks back, I bought a 98 LT that, according to the previous owner, had an issue with shifting into reverse until it was warmed up. Pretty sure I got that problem taken care of. Noticed that it was difficult to turn (like the brakes were hanging up), so I took it to my local Meineke shop to have them check out the brakes. Brakes weren't causing my issue. Anyhow, I was pulling a hill a couple days ago and I've lost 3rd and 4th gear. The fluid is as black as diesel oil. I manage to get towed home (108 miles away when it died) thanks to a good friend of mine, and while we were in transit back, we were discussing the possibility the transfer case was still engaged. (NP233 transfer case) so it backed off the dolly with the rear driveshaft disconnected, so guess what caused my tranny to fail? So, I know you're thinking, "well, ya big dummy, why in the *expletive deleted* didnt you disengage the GD transfer case?" Well folks, here's where the gremlins lives. I have no lights for my transfer case. I've checked all fuses, all are fine. Have not checked the TCCM. Also have not checked the wires on the case itself. Now for my question: In your opinion, would I be better off getting a used trans and transfer case and try to tackle these issues afterward? It only has 160K on it and don't want to send it to the boneyard.

 

If you need the truck, i would swap what you need into it, lock it in 2wd and drive it until you can figure out the gremlin.
You can either have someone rebuild the trans (usually around $1000-$1500 for a bench job) or get a used one depending on your budget. If it were me id get a junkyard trans with the longest warranty i can find and run it. Hell, im running a $500 junkyard 4l60E in my v8 swapped blazer. A rebuilt unit does usually have a much longer warranty and better piece of mind though.

As for the transfer case, are you sure you need to replace it? 4wd transfer cases rarely fail unless they actually break the case or stretch the chain too far. These truck are however known for the electric motor that control the transfer case to fail.
If you want to get it out of 4wd, there should be 3 10mm bolts and one plug holding that electric motor on. Its located right next to the front driveshaft. Once you remove it you can turn the shaft with vice grips. i have done this a couple times years ago to drive in the snow when my dads 97 blazer was having issues with that motor

Edit: Have you tried just unhooking the battery cables and touching them together to reset the TCCM? This has worked for a few people with the same issue you are having of no lights on the 4wd switch.

 

The battery was just changed, so I would think it would have reset itself when that happened, however, I am willing to try anything to get it to work. I still need to check the wiring to the TCCM and verify that is all good. Now, this vice grip method you speak of, which way would I turn this to get it into 2wd? Manually engaging/disengaging a transfer case like this is a new animal to me.

 

Check the ATC fuse in the underhood relay center. If still no lights, check for 12V on the large red wire at the TCCM. Pull the connector off and inspect for corrosion, a common problem. TCCM drives the lights in the buttons as well as the encoder motor. But not going to do you much good until the trans is fixed.

 

I had thought of the ATC fuse and had checked that... all applicable fuses, to include the 4x4 and illumination fuses as well, are good. I do have 1st and 2nd gear but the vehicle is parked until I determine my course of action.

 

In not sure what direction to turn it (I believe its clockwise all the way to 2wd), however, you should be able to turn the front driveshaft freely when the transfer case is in 2wd because the front axle disconnect should disconnect. The CAD is controlled by a vacuum switch located right next to the electric motor on the transfer case.
If you google an image of a NP233 you will see the small black switch with 3 vacuum ports on it.


Once you have the electric motor off of it you should be able to turn it and feel 4 distinct detents, 2hi, neutral, 4hi, 4low