History:
I have the 3 button transfer case switch on my 98 Blazer. This winter I had some 4WD issues which initially turned out to be a vacuum problem. I had some cracked hoses and upon replacement everything seemed to work fine.

A week or so later, I noticed the front end getting very noisy, making all sorts of weird grinding noises on occasion. I noticed this problem went away by hitting the 4HI switch then eventually going back to 2HI. Soon after my switches stopped responding to my commands, only working (on occasion) if the truck was in netural. I took it to Aamco for a health check and they informed me that my TCCM was not communicating with their scan tool and that I would need a new one. I don't have the $$ for a new one so I am searching for a used part which is tested to be working.

There is one thing which troubles me about this though. Usually the truck is noise free in 2WD, however I've noticed something weird happens after reversing from or pulling into a parking space if I turn the wheel all the way. After being in full lock and then driving off the grinding starts immediately from the transfer case like the 4wd is somehow magically partially engaged. This is a strange problem to me so I don't know why turning the wheel hard over would cause this. To get it to stop is difficult and usually involves several iterations of going into neutral, hitting 2wd, then going into drive.

Since this problem doesn't seem to fit exactly into any regular diagnosis, any thoughts?

 

Check out this thread:
4wd Front Axle Clicking When in 2HI - Goes Away when in 4HI/4LO

This could work in reverse if there is a problem with the engagement cable that does not allow it to release all the way and/or engage all the way.

 

Could be. I will investigate what I can. It's strange that the problem is immediately brought on by lock turns of the wheel when getting out of parking lots.

 

I should add that if in 4WD (when it wants to work), turning hard into a parking spot or something has resulted in a loud bang before... as if I hit something under the truck. Something is moving around down there that should not be!

 

You shouldn't be doing tight turning on dry pavement with the truck in 4wd. That is asking for problems.

 

Never thought about that before because I honestly didn't know it would cause any issues. Though I've only actually done it a couple of times.

I take it that it causes issues with the mating mechanism for the front axle?

 

Well, it causes the drivetrain to bind up. If done repeatedly, *things* will break. And by *things*, I am talking about the weakest link. Could be the collar inside the front diff snapping in half. Could be a u-joint failure. Could be something internal to the transfer case. It is just not a good idea to be driving with 4wd locked in on dry or even wet pavement if you are going to be doing tight turns.

 

from my under standing you do not pull code with the scan tool for the transfer case problems. if you ground pin 13 at the
DRL turn the key on with the engine off count the flashes of the 4wd selector buttons you should come up with blinking lights or codes 1-4 I have to look up what the codes mean

there is also a fault sequence to fallow if interested let me know

 

DLC, not DRL.

And this process is covered in the thread linked to below:
OBD2 Non-Automatic Transfer Case Diagnostics
Amongst other very informative threads located in the Tech Article (DIY) section.

 

After some digging it really does look like it is indeed the springs in the axle that could be at fault. I don't have the time or the tools right now to investigate further so I guess I will take the Blazer to a shop. But this repair sounds rather expensive from a labor stand point and I am wondering where the individual parts could be sourced from. Ideas?