Sounds like the encoder is locked up, the clicking is coming from the passengers footwell in the kick panel.

 

Its coming from the TCCM. When we unplug the TCCM all the lights go out on the push buttons, when its plugged in they come back on but still lights up the 4wd.

So you think the TCCM is bad or encoder or both?

How often has anyone seen the seal go bad in transfer case and leak fluid into the transmission?

Is there supposed to automatic transmission fluid in the transfer case?

 

Also, can I take a TCCM from an older Blazer? I think there is one next door that is a few years older than my 99

 

yes the 233 3 button TC has automatic trans fluid, if you remove the top plug on transfer case and fluid is pouring out thats a sign your seal should be replaced.

one way you can tell if your in 4x4 is by turning the engine on and jacking up the front passenger tire, try to turn the tire if it spins freely the front axle is not engaged. if it doesn't that means the front actuator is getting vacuum to pull the cable and engage the axle. did you ever check the vacuum switch on the transfer case? if your overfilled with fluid in the TC it will eventually suck up the vacuum lines and can get into your HVAC system and cause a whole mess of problems

not sure if older parts are interchangeable, could always go ebay route and return if its not the problem find a place that does not hassle. thats what i did with my 2000 Blazer 4x4 problem

 

Last time we removed the top plug, we couldn't feel any fluid, so we topped it off.

Is it possible for the fluid to drain into the transmission? If not then the guy who rebuilt the transmission put it more than he was supposed too, its about 3/4" over the line on the dipstick. Few months ago we filled the TC and now it was over a quart low and there no leaks.

We replaced that switch the first time around, the ball bearing wouldn't move, if thats what its called, but when we replaced it, 4 wheel drive engaged properly.

 

The transmission is under pressure, so no it can't drain into it.

 

So why is the transfer case low every few months? There are no leaks at or around the transfer case. Only leak on the Blazer was the front axle which is now fixed.

 

My 2000 blazer is stuck in 4 wheel drive. Will run in 4 low and 4 high shifts into 2wd but won't stay engaged.

 

Start a new thread. 3 button or 4-button (auto) switch? Won't stay engaged in what? Please rephrase and explain your issues and observations clearly and in detail.