I recently bought a 2000 blazer (trailblazer).

After a couple of weeks I noticed it seemed to be "slipping out of 2wd. I started by replacing the rear axle suspecting missing teeth on the ring gear or something.... not to mention the dust sheilds were basically non-existant due to rust. Anyhow, Not the problem... but It did help me find a faulty brake line.

All in all I guess it was a good thing. I have a newer rear axle with new oil seals and fresh fluid.

Plus I fixed the main brake line to the rear. Now after All this was fixed I went out for a drive up and down the alley only to have it "slip out of gear" The difference this time was I could actually hear the slipping. I got out of the truck while it was slipping in (N).. Sounded to be coming from the transfer case and upon touching it I could feel a vibration.
So here we are... I got a Transfer case from a very generous member (okiedoak20)

Today I pulled the old TC out and Tomorrow Ill attempt to reinstall the functioning TC.

Anyways Id like to start some discussion on this rarely talked about topic of transfer cases. Ill be disecting the old one to figure out exactly where I was having a problem. Ill take pics and talk a little about my experience. Hopefully someone else in the future will be able to use some of what I post here.

I encourage anyone else who has ever had any TC problems to share as well.

My symptoms were: Every once in a while my truck would just slip out of 2wd. Basically It was like the truck was in (N). No noise whatsoever and once I hit 4wd the front wheels did all the work and eventually Id get my rear wheel drive back.

I will continue to keep this thread updated with more pics as I get around to stripping the old TC down and seeing just how it works.

 

The only thing that would cause it to drop the rear output would be a range shift into neutral as you said, but that wouldn't allow the front output to pull you along since neutral is up in the range box portion of the transfer case which is prior to the chain for the front output. It'll be interesting to see what you find inside. It has been a long time since I tore apart an NV236 transfer case and I didn't have time to take pictures. It was just a clutch replacement and back together.

Attached you'll find a few parts explosion views of an NP/NV246 which is used in the fullsize truck and is just the big brother to the NP/NV236. As you can see, the rear output shaft is splined into the planetary gear set which is what gives you the hi/lo ranges as well as neutral. The clutch pack is mounted to the rear output shaft, the carrier for the clutch pack is splined to drive the upper sprocket for the chain which powers the front output.

*Images courtesy of Drivetrain.com*

 

Im guessing something in the planetary or something around that area.. We shall see..... I could definitely hear something that sounded like a small (lots of teeth) gear slipping against another gear.. Very interested myself... I actually found a complete breakdown somewhere for tear down and rebuild for the 243. Still very few and far between for relevant info on my particular problem... I have a NP236 although Im sure the 236 and the 243 are extremely similar. More pictures to follow..

 

The range portion of the 243 (big brother to the 233) is nearly the same as the 236. The major difference is in the clutch pack on the sprocket for the front output in the 246/236.

As far as the differences between the 236 & 246, the 246 has a stronger (more gear teeth) planetary setup as well as more clutches in the clutch pack to allow for the higher torque rating. I haven't tried this myself, but I know that the Syclone/Typhoon croud have put more clutches into the 136 (a 236 w/o the planetary range portion for hi/lo) for added holding power effectively making it into a 146 (a 246 w/o the range portion).

 

hoho! i'm subscribing to this, my father has an 06' Tahoe and about a month ago he had the exact symptoms with his t-case. He said that he had an unknown vibration coming from underneath his center console for the past year or so, then recently his would shift out of 2wd and go to neutral. The truck would also engage 4wd automatically at times upon start up ( i guess this was a failsafe feature to keep it going at times). He took it to a dealership and they replaced it for him as they didn't know what was wrong with it.

 

omg! man i have the exact same truck, color,trim level, wheels everthing! i even painted my wheels duplicolor graphite! small word huh. heated everything=niiiccceee:0

 

Update:
The transfer case has been in for a couple of weeks. Things seem to be better. I still have a vibration. I believe its probably a combination of the 140k ball joints and worn suspension. I have new shocks coming this week and I guess ball joints should be replaced at the same time although I have not ordered any yet.
Now after looking at those breakdowns again Im going to try and take out the C clip from the transfer case and see what was wrong. Thanks swartlkk for those transfer case breakdowns. Ill try to get some more pics once I crack it open. May even try to rebuild if I think I can. Anyhow This is the only pic I have. From the transfer case going into the truck.
Oh and got a K&N intake kit coming in the mail too =)

 

Okay, Yesterday I tore into the transfer case and started removing C clips throughout. Basically dissecting it piece by piece. I havent found anything yet. I did notice however that the filter seen in the last picture seems to be clogged with some sort of debris. Im not sure if that could have led to a malfunction, but it seems possible. Ill investigate that later.
Unfortunately I needed a large allen wrench last night to get into it any further, so I quit for the night. It was chilly anyhow. Today is sunny and 62 degrees. So Ill dig further, plus my K&N should be here today also. Heres some pics Ill post more as I get them.

EDIT: Just checked and I dont have an allen wrench large enough.. Anyone know what size it is I need. Ive got to remove that swing arm piece to the left in the first pic. Thanks