Ok so my 98 envoy , I took it to the beach as i usually do and go to engage 4wd and just get clicks and flashing lights , so i just started changing parts like a idiot...
so heres what ive changed/found out so far just to get them out of the way
Encoder Motor New Reman
Switch on Front Diff New
Vac switch on TC New
TCCM Used Know good
Cable is not broken
Vac Actuator Good , held vacuum no problem
I am Getting vacuum from the engine to the Vac switch on TC
When i try to engage 4wd i am getting no vacuum to the actuator

So My only thought now . Is it pobbilbe that whatever peice inside the TC that presses the button on the vac switch is broken? or is it just something that could never break ?

Any ideas?
And yes i reset the TCCM after every part i changed and after everytime i try to engage the 4wd .. i think it just shuts down and dosent even try after you attempt 5 times or so , am i right?

thanks -Dan

 

Did you pull rhe DTC codes from the TCCM before yyou replaced it
I had a issue the service 4wd drive light would come on all the time
the GM prts guy was cool and pluged his TECH 2 scanner and pulled a 3725 DTC code from the TCCM
I replaced the switch on the dash and re plumed the vaccume lines the guy that had the 99 s10 blazer and it all missed up
put the old TCCM back in and pull the codes
any good trammy shop will do it for free if they think they are going to get the job of fixing it
they MUST usr the TECH 2 Scanner
Good luck

 

the 4wd dash light is not coming on , just the lights on the switch ..
im trying to figure out why i can get vacuum to the vac switch but not to the actuator

 

pull the vac line and see if it sucks at the acatuator