1994 gmc sonoma 4x4

[gcochran223]

94 sonoma sle 4.3 push button 4x4 problems.

4x4 hasnt worked since i bought it a month ago. i replaced the $20 switch on the dash cause the bulbs were so dim and the 4x4 didnt work regardless. when i push it into 4hi or low i can hear the tccm click and when in 4lo i can tell it is engaged. i went to use 4hi yesterday in the yard and my front was not engaged in 4hi, i did not try 4lo.

 today i pulled off the battery tray and recorded as i tried to engage the 4 wheel in both and the vacuum actuator does not move but i can move the cable freely by hand so it doesnt seem to be locked up. i disconnected the vacuum feed to the vacuum actuator and when trying to engage in 4 wheel i did not feel any vacuum over the hose.

-how much vacuum can you feel over this? is it noticeable?
- and is it safe to assume the vacuum switch on the tcase is bad or is there more troubleshooting possible?

thanks for any info

[Irish_Alley]

the only thing i know about them is they are vacuumed controlled i would put a vacuum gun (dont know the technical name for it) on it and see if you can do it with the gun. are your hoses in good condition

[FlatBlack77]

check the hoses as much as you can try to check the entire legth of them they could be dry rotted and slip open.

you should be able to feel at least a little something from the hose

[gcochran223]

Yeah there wasn't anything coming out of the hose. After an hour of reading I found a solution to make it cable controlled. Or since its one wheel in the front I could just lock in the front full time. Thanks for the responses fellas

[Engineer]

I just replaced the vacuum switch on the transfer case on my '97 Blazer.

It fixed my problem. Have had to replace the vacuum actuator under the battery before as well.

And have also had to fix leaky vacuum lines.

At 300,000mi, I can't complain about my Blazer overall, but the 4x4 system has been a pita.