So the front axle isn't engaging. The transfer case is working. I get 4-hi and 4-lo, but the front axle isn't engaging.

The last time this happened I checked the connections down on the axle, cleaned everything up (had oil and junk on the connector) and it started working.

I think I might have a vacuum leak up top somewhere, but I could not isolate it.

What do I check...? How do I test the actuator...? Looks like the actuator is about $50 from AdvanceAuto......

What is the common ailment here...?

Thanks.

 

This problem is documented in a LOT of posts.

Basically, with a hand vacuum pump and a vacuum pressure gauge, you can test things out at the actuator. You can test engine vacuum level with the vacuum gauge connected to a vacuum source on the engine. You can then test the vacuum level at the actuator when the transfer case is in 4HI or 4LO. They should be similar. You can pull a vacuum on the actuator with the pump and make sure that it can pull the cable fully (1/2" to 3/4") with the vacuum pressure that the engine can produce. Once you pull a vacuum on the actuator, it should not decrease. If it does, you have a leak.

Actuator is located under the battery.

 

Thanks. I do know how to use a vacuum gauge.....

Underhood there isn't a plethora of ports, but some long runs of hose. I have good ported vacuun at the intake. I haven't taken a reading on the lines yet because they are brittle and I don't have enough laying around the house to replace if they crumble while taking them off the fittings.

I'll get hose today and try and find the source of the problem. Might pick up an actuator just in case that doesn't fix it. I don't want to be outside doing troubleshooting if I don't have to.

 

Might check the Front Axle Actuator Valve on the firewall above the distributor. I had the same vacuum problem and when I replaced it, it works fine. Had to go to the dealer for it though (P/N 15165891).

 

My friend dealt with his then had more problems. This is what I learned.
1. There is a vacuum reservoir attached to the underneath of the hood, close to the hinge on the drivers side. The vacuum line that goes to the back of it fell off.
2. The transfer case selector cable attaches to the vacuum actuator under the battery. The end of the cable attaches to a bracket with built in "ears" that keep it in place. They are week and brake off easily. They can be replaced with a small hose clamp.
3. I could reach down under the battery while someone else pushed the button in the Blazer and feel if the actuator was working.
I hope this helps.

 

THANK YOU THANK YOU THANKS

My hose didn't fall out it broke off because is was 13 years old, just took the old girl down the snow covered road and it was great having the 4 wheels working again

 

Glad you got it all fixed up!

 

Good job fixing it yourself! Not that mechanics shouldn't have a job, it's just nice to see a DIY work out.