4wd issues

[nautiduck]

Is there anybody on here really familiar with 99 chevy 4wd systems? I have a 99 K2500 (old body style) 4wd crew cab automatic with the push button transfer case 2hi 4hi 4lo. Yesterday I was pulling a trailer with my tractor on it and I looked down and the 4lo button was blinking. I pulled over shifted to neutral and hit the 2hi button, nothing I hit the 4 hi button and I heard it clunk like it was shifting into 4wd and then it clunked again (2 sec between) both 4 hi and lo lights were blinking then the 4 hi stopped. I tried this several times with similar results. Today after a bit of research I pulled all three fuses related to the 4wd and transfer case and pulled the plug to the actuator and plugged it back in. Now the lights come on on the switch when I start the truck but then they all go off. Is there any way to test the components without replacing every thing? I pulled the actuator it looks fine with no broken pieces. Does anyone know what voltages to which pins to check for function? Please help I cant afford to take it in to a dealer and I dont know any other mechanics in the area that are worth a crap (Hell my local dealer isnt either). I can fix it myself with a little info.

[whitey]

It sounds like the switching motor in your transfer case is jammed up. It is very common on GM vehicles. Go under the truck and tap on the motor with a hammer and it should start working.

[nautiduck]

Do you mean the actuator or is there another motor that your talking about? Ive pulled the actuator its one of the plastic housed servo operated types its not thermal like the old style.

[whitey]

Are you talking about the actuator on the front differential or the transfer case? Thier should be a motor on the transfer case. Thats what im talking about.

[Delmer]

you may be able to find some help here

http://www.nc4x4.com/forums/index.php

[nautiduck]

Sorry Whitey I was talking about front diff. I didnt know there was a motor on the transfer case.

[maritime23]

Just had this happen to my S10, when I hit the switch the 4wd lightrs would only blink and nothing would happen. Took the truck to the shop and found out the it was a vaccum problem on the fire wall of the vehicle. was told it was very common for the hose to rot at this connection. Cut back the hose and plugged it back in and what do you know it worked, light stopped blinking and the 4wd worked with no problem. Simple solution, connection was back on the fire wall by the distributor cap. This might be the problem who knows, give it a try and good luck.

Maritime23

[maritime23]

Just talked to the guy that did the work, Look on top of the transfer case thats where the vaccum hose is suppose to come off and make its way up the the fire wall.

Again Good Luck

Maritime23

[whitey]

The actuator on the front diff that you checked out is used to engage the front diff when 4x4 is selected. Thier is also a motor bolted to the side of the transfer that should have a 5 or 6 wire plug going to it. That is what switches the transfer case to the differant ranges. It is a very common problem for them to jam up between gears. Sometimes you can tap them with a hammer and they free up. If you give me the year body, style and engine size of your truck I can look up some info on it when I get into the shop tomorrow.

[nautiduck]

Hey whitey thanks it is 1999 (c/k old body style with the rectangular headlights) K2500 crew cab 5.7 ltr.

I could hear it trying to shift yesterday and today since I unplugged the actuator and pulled and replaced the fuses I got nothing. I pulled the plug to check for corrosion and the same with the fuses and to make sure they werent burnt. there doesnt seem to be any broken or corroded wires. I called the dealer to ask them and they said was possible I tripped something ( I dont remember what she called it) and that I needed to bring it in to reset it.

Thanks again till I find another full time job I cant pay dealer (or any mechanic) rates. I really appreciate the help.