New member with transfer case problem

[suburbanfrustration]

Hi, new here hoping someone can help. I have a 99 suburban with gm246 transfer case. It won't shift into 4Lo. Shifts between 2Hi and 4Hi fine. I tore apart the transfer case and everything looked ok except had the wrong fluid in it. Encoder motor shifted between 2Hi and 4Hi when removed from transfer case but wouldn't even try to shift to 4Lo. 4Lo light just blinks. Re-installed transfer case with correct Auto-Trak II fluid and installed new encoder motor. Still no 4Lo. Transmission is in neutral when trying to make the shift. Is it the TCCM or could it be a bad speed sensor not indicating speed less than 5mph? When shift is made between 2Hi and 4Hi and back I can hear a click in the dash I am assuming coming from the TCCM. I don't hear this when trying to shift into 4Lo. Thanks.

[suburbanfrustration]

I also replaced the 4wd buttons. I think this problem started when I mistakenly tried to shift into low range while driving in gear possibly over 5mph. I had just bought the rig and didn't know you were supposed to be in neutral. But the internals of the transfer case looked ok. Could the TCCM have locked me out of low range? I tried removing the battery cable to clear any falults. Is there a way to reset the TCCM if it did lock out 4Lo?

[02suburbanZ71]

I also replaced the 4wd buttons. I think this problem started when I mistakenly tried to shift into low range while driving in gear possibly over 5mph. I had just bought the rig and didn't know you were supposed to be in neutral. But the internals of the transfer case looked ok. Could the TCCM have locked me out of low range? I tried removing the battery cable to clear any falults. Is there a way to reset the TCCM if it did lock out 4Lo?

It doesn't matter if you put it in low range going fast. The computer will not allow it to engage unless its in neutral so you cant mess that up. I've done it many times without an issue

[02suburbanZ71]

It doesn't matter if you put it in low range going fast. The computer will not allow it to engage unless its in neutral so you cant mess that up. I've done it many times without an issue

Find a tech 2

[gmtech4]

you need to scan it and either follow the diag table yourself (which you will be shut down by step 2 i believe) or let the shop diag it for you

 

you sure have done alot of work for nothing

 

reply with the code #

[suburbanfrustration]

You are right.

[gmtech4]

i know ,,,,lol

[suburbanfrustration]

It was a real pain but not quite all for nothing. The switches were bad to begin with, a bad connection. When you flexed the switch it would start working. And in the process of all this I got a better understanding of how the t-case works. I did get the wear plate installed behind the pump before it turned into a problem.

[suburbanfrustration]

And I learned about the need for Auto-Trak II fluid which was not in it. Hopefully the correct fluid will cure the aggressive tire on pavement noise I occasionally heard while driving. It doesn't have aggressive tires.