Hey ive done alot of research and have been reading alot of these threads (probably spent 2 hours reading) and so far i havent seen a problem like mine, my service 4wd light came on today for the first time ever, my service engine light has been on since i purchased the truck but it never idled or drove rough so i payed no attention to it. anyways now the truck doesnt want to shift from 2wd to 4hi or 4lo or even 4auto, ive read that i need to get it scanned but i was wondering if that was my only option? The other day i left my house late at night and weve been having fluctuating weather, so when i left i heard a loud clunck come from the front end, i thought it was just me frozen in ice or something. but like i said now my service 4wd light is on. could this be linked? also my uncle said it could possibly be my transmission that is faulty? hes a mechanic of 40+ years just hoping hes wrong... Thanks in advance!

 

Update, today went over to my buddys house had a look at it with his dad and we checked to see if the selenoid on the front diff was getting power, it is getting 12v so dont know if that matters or not, also when i took off the front passenger side was knocking and did it again as i was slowing down, but the longer i drove the less it did it.

 

There is a 4x diagnoses write up under the tech section...that may help you out.
The noise your hearing dwf makes it diff from any problem i have ever exp with my ride.

 

thanks for the reply, have been on here for the past 3 hours looking up "service 4wd" and encoder motor and such, still havent seen anything like my issues, im just scared to bring it to gm to be read as im a student and on a very tight budget!

 

So now it will attempt to go into 4hi, the light flickers but the only way to get it to do so is to hit 4auto then 4hi. the transfer case was replaced by the previous owner last year, she said she was having the same problem, replace the tcase and hadent had an issue since, yet i bought it at a steal, and am now having doubts as to her honesty... how much would a new tccm cost, as well as an encoder motor and how much labor am i looking at to do it all myself?

 

Shift Motor Replacement:

How To- Replace T-case shift motor - Zr2USA.com

Shift Motor Cost:

NV236 Transfer Case Shift Motor for Autotrac T-cases

Not sure about the TCCM cost, but it's not hard to get to and prolly just wiring harnesses to connect.

 

Well that turns out NY transfer case was almost out of oil, by almost I mean just enough to get the bottom of my margarine container wet. Filled it up and got it to go in 4x4 then had to turn on and off to get back ti 2hi now i can't get it back to 4x4

 

Well my TCCM is corroded, as is the harness, going to try and find a used one even though im a little scared to buy a used one since its a common problem. hopefully i dont have to spend more then 500$!

 

Well, that sucks...never understood why GM would want to locate an electronic componennt in an area known to attract moisture.

 

Anybody ever buy a tccm off eBay? Should I stay away? I might just fix it and sell it so if the eBay one id ganna work fir a little while I'm fine with that. Thanks