there's a vacum switch on my 86 that's on the top of the transfer case between it and the floor board. that switch operates a diaphragm located on the passenger fender well near the battery in the engine compartment. that diaphragm in turn is hooked to a cable that goes to the front axle, and engages. it. your problem could be the switch on the transfer case. that was the case on mine, and I decided that it was easier to route a manual vacum pump from the cab to that diaphragm to engage the front end than it would be to try to change out that switch. not reccomending this, just offering other possiblilites.
On my 94 S10 Blazer the vacuum diaphragm is under the battery tray. You have to remove the battery and the tray to access the diaphragm.
It may have the original transfer case that was recalled
there are many things that could potentially be wrong with your case. can u engage your 4wheel?
My f150 shifts from 2wheel to 4wheel on the fly, but to use 4low you need to be stopped with your transmission in neutral to engage the low range in my transfer case.
If the shift lever on the floor won't move to engage there is most likely a linkage problem. If the linkage seems to move and you shift the lever under the dash from 2wd to 4wd and the transfer case does not engage look for a vacuum problem. the lines can be very brittle and break easily. There is a vacuum motor on the transfer case that must work in order to engage the 4wd. if all of these seem to work then the problem is likely to be internal.
To engage 4-wheel drive (engine running), you should put the transmission into "Neutral" and manually engage it with the manual transfer knob located to the left of the auto/manual shifter. up/left is 2wheel "high", down/left is 4wheel "high", up/right is transfer case "neutral", and down/right is 4wheel "low". Once you engage your setting selected, look for a green "I" like icon in the bottom right ofyour gauge cluster showing that you are in 4wd. You may have difficulty making this icon appear, just hold brake and move your shifter into drive then into reverse and back to drive. If you cannot achieve engagement, contact your nearest service technician.
All that you do if put the shifter in the four wheel drive position.
check vaccum lines on differential or by shift linkage
If it is 89 to 95 it has a central axle disconnect, they go out all the time. Check that.
update the front axle actuator. GM has a new kit which requires you to replace the old style front axle actuator (metal shell) with a new style plastic metal actuator and update a wire harness, splicing into the brown wire at the transfer case connector. Also check the 4wd fuse just for grins.
Most four-wheel-drive vehicles are controlled by the transfer case. The transfer case has many years in it. A bad year in the transfer case will cause the vehicle not to engage.
put trans in neutral and put 4wheel in gear then go to drive in stop mode only
Well is it actually engaging into 4WD? If so, then you do simply have a problem with the lights. However, if you don't notice the transfer case engage, you may have a problem with either the push button system or the transfer case itself.