Hi guys,

I got the following problem, I can't get my truck into 4hi, 4low or Auto. If I'm in neutral rolling at about 2mph and hit the 4low button I hear a clunk, but the blinking light never stops. I feel the truck jerking around when I push the gas but it doesn't feel like it's in 4x4 correctly. If I press the auto switch, it will just stop blinking after about 30 seconds and then go back to 2wd. If I press the 4hi button it will just blink without ever going backt to the 2hi, even though ut never engauges. When I first testdrove the car before buying it I was able to put it into 4hi without any trouble and back to 2hi, that was about a month ago and now that I wanted to engauge it today because of the snow, no chance at all. I searche around and triedchecking if it was the switch inside the car but that was a no go, and the fuse is intakt too. Would I hear a clunking too if it goes into 4hi or only in 4low? Anyone have any ideas of things I could test out befor I give up and take it to a mechanic?

It's a 2000 blazer LT, 4 Door with auto, 2hi,4hi,4low with 100k miles on it.I'm the sencond owner, and the previous owner was an older gentleman, and I doubt he was going offroading like crazy.

Thanks
Cedric

 

The first thing I would try would be to pull the TCCM (located behind the passenger side kick panel) and clean the socket and plug. Often times this connection will get corroded and cause these problems you have listed.

If that does not solve the problem, then the TCCM codes must be read. This is only possible with a Tech2 (dealer) or equivalent scanner as the TCCM for the Auto4WD optioned trucks is an serial data communication device.

 

I located the TCCM and there was one corroded pin on the black connector that goes into it, cleaned it up, both pin and connector but without any change. Still have the same non reacting of my 4x4. Any other ideas? Worst case scenario, how much will a repair of the 4x4 cost me approx? Thanks Cedric

 

Ok I tried listening to the sound it makes when you push the 4hi button and back to 2hi. When I kneel next to the driver side door and listen to the sounds that come from under the car I get this "pffffft" sound when 4hi is pushed and 2hi. It sounds like there is an air leak. I don't know if this is a normal sound but I doubt it. Could this mean I need the vacume switch replaced? I'm trying to figure out as much as I can as I honostly don't trust mechanics anymore as one almoste ripped me off again, read my other thread and you'll know what I mean.

Thanks a lot.
Cedric

 

Dude! I had the exact same problem w/ my 2001 LT,
here's what my mechanic found:
solenoid on transfer case for front differential operation.
He replaced and restored 4x4 operation.
good luck

 

hey man, how much did that run you?

 

Double check the fluid level in the cases. I had the same problem last year.

 

Alright, it was the vacume switch. Got it fixed and all works like a charm

 

Thats good, got it fixed before I could respond with the switch. I just got my 4x4 working today and want to get out in the mud to see how bad I can get her stuck. Im up near elgin.

 

I was just glad I had it 30 mins ago when I went shopping, kinda slippery out there right now But it works like a charm!