i have a 2002 gmc jimmy 4.3 4x4 with auto 4x4, 4hi, and 4 lo. I press 4hi and the light blinks nothing happens, put it in neutral and press 4lo you can hear the transfercase shift but the light just blinks, then press 4hi after and you can hear it shift again but still blinks, then press 2hi no sound and the light stops blinking. Could it be the electric shift motor on the transfer case or what? Its driving me insane!

 

search it is almost the most common thing on the forum

 

*Moving to 2nd Gen Tech*

It is likely a vacuum switch problem. Check for vacuum at the front axle vacuum solenoid on the firewall. If you have vacuum there while you press the 2hi button, then your vacuum switch on the transfer case is bad.

For other trouble shooting steps, please try a few searches. As eluded to above, you are not the first to have 4wd problems.

 

are there any pictures or anything that can show what exactly im looking for? I replaced the actuator under the battery how many more are there? also i heard theres something under the right kick pannel?

 

Did you try the search feature???

 

yeah i did and still found nothing, i dont know if im searching the right thing or right area or what

 

"vacuum switch" Maybe constrain it to a author name...

THIS THREAD has a picture of the transfer case and an explanation of where the switch is.

HERE is a good thread by Tim (hanr3) about the 4wd systems in these trucks.

Both of these threads were on the first 2 pages of the aforementioned search. Searching can sometimes be an art.

 

thanks i think i saw the solenoid you were talking about, little black thing two hoses going into it? Which one do i pull off to check for vacuum and do i need a tester or can i use like my finger or something? Cause i just put my truck in RUN and pressed 4hi and 4 lo and i can hear the motor and it sounds like its going in and out after i switch from lo to hi.

 

i just went out to my truck checked all the 4x4 and transfer case fuses all were good and i checked to see if it still makes a noise and this is what happens:
Starting from 2hi - neutral - 4 lo = makes a gunk sound
2 hi - neutral - 4 lo (gunk sound) - 4 hi = another gunk sound
2 hi - 4 hi = nothing light blinks
2 hi - netrual - 4 hi = nothing light blinks

4hi doesnt make a sound unless its in neutral and in 4 lo already, what could this mean?

 

The only time you will get a clunk (or gunk) sound is when the transfer case changes ranges. You have gear sets that are meshing together to make the change in gear ratio. The transition from 2hi to 4hi or 4hi to 2hi will not have the same sound. There could be a sound when making the transition from neutral to any one of the modes due to the engagement of the gear sets for the selected mode when coming out of neutral.

I have always found that these transfer cases shift a lot better (more repeatably) when you are slightly moving. Put the transmission into neutral while rolling slightly and select the desired mode to transfer into. See if that changes things.