4X4 engauging, not working

1995 blazer 4dr 4wd w engine.

It just snowed today and i thought i would test out my 4 WD. i hit the 4hi button and i heared the transfer case engaging it. i then went to go foward and it just spun the back tires. i thought that maybe it took a while to engauge fully. so i let it run for another 5 mins. i went back to the car and same story. i tried going up a hill and didnt go anywhere but backwards. what do you guys think??

check your vacum lines. Make sure that they have not popped off or maybe broke. That would be the first place to check. Also do you have electronic or manual shifter for the 4 wheel drive? Do the lights blink at all? Could be actuator, vacum lines, encoder, or something else. SDo if you can check the lights post back also. Also if you can use the search function and search the forum for 4x4. There are a lot of posts on this forum related to 4 wheel drive problems but if you can't find anything that helps just keep asking and posting up to date info.

It will be 1 of 3 things, either the vac actuator under the battery is torn (or clip fell off), the vac hose leading from the actuator to the transfer case, or the vac switch on the transfer case.

I have had a problem with my 4x4 and it turned out to be the motor on the transfercase. Your problem sounds like the vacuum switch under the battery. check and see if it folds in when you start the blazer. check the line going from the vacuum port behind the motor to the switch then from the switch to the frunt of the transfer case. If all else fails and it turns out to be the encoder module i have 2 good working ones. This is also a common problem. It is also possible to be the vacuum switch on top of the transfer case or the encoder motor. Give it a look and post back to us. Hope this helps

rlith helped me find my problem. It was the vac servo under my battery tray. it had a tear in the rubber. ordered another and i will post reply to tell if everything is fine. Thanks all

i am having the same problem with my 2000 blazer. It is is the shop right now getting the oil cooler lines getting fixed. But when i push mine to go to 4 high it just flashes then when i push it to go to 2 wheel it will right at the last minute it will kick into 4 wheel then go to 2 wheel. Any ideas on what this could be and how much to fix? Thanks for the help in advanced.

i am having the same problem with my 2000 blazer. It is is the shop right now getting the oil cooler lines getting fixed. But when i push mine to go to 4 high it just flashes then when i push it to go to 2 wheel it will right at the last minute it will kick into 4 wheel then go to 2 wheel. Any ideas on what this could be and how much to fix? Thanks for the help in advanced.

In your case I would lean more towards the encoder motor or vac switch on top of the transfer case (more likely the encoder motor). Though try resetting your ECM (disconnect the battery for a 1/2 hour) and see if that fixes it.

OK cool...someone else told me that it could be the switch. The thing that makes me think it is something wrong with the switch is that if i unplug the stiwth from inside the car the service 4 wheel drive light does not come on. I just installed a aftermarket radio and had to undo my 4x4 switch and battery so i am going to try disconnecting my battery for 30 minutes.

If disconnecting the battery dosent work you will might need a encoder module. this is the most common thing that needs replacing. I had the same problem however it turned out to be the encoder motor. the module gets "logic lock" sometimes and the battery trick fixes it. however a surge of current to either the module or the encoder motor will Short it out and then need replacing. At the dealier costs $400 for the encoder module and at your local parts store $200 for the encoder motor. I have an encoder module that ill sell you for $125 and ship it to you for free if you need it let me know. Good luck Tony...