I have a '97 Blazer with about 100k miles. Got a little snow and hit the 4H button and the transfer case shifted but the front end isn't engaging. I also tried 4L and the transfer case shifted fine but I get the same thing. I removed the battery to check the vacuum line on the actuator ( I think thats what it's called) and it seems secure. Any suggestions as to where to go from here would be appreciated!
Thanks in advance.
"Andy M." wrote
That vacuum line goes back to a switch on the transfer case. You need to make sure that the vacuum source line to the switch has engine vacuum at all times. Then you need to check and see if the switch is routing vacuum up to the front diff actuator when you engage 4hi. The easiest way to check this is to pull the vacuum harness off at the t/case, while the engine is running, see if you have vacuum at one of the three ports, if so, connect that port to one of the other two and see if the front diff engages (you can try one then the other). If so, you have a switch problem, if not, then you may have a broken vacuum line somewhere.
Ian
Can you feel any suction from the line? It just being there...
~KJ~
an S-10? Not familiar with the newer models (have a 91) Do they have a lever actuated vacuum switch mounted on the transfer case?
(aftermarket, about 30 bucks)
To check for a bad switch, get it off the ground, hook up a hand-vacuum pump to the line going to the diaphragm unit, start it up, put it in 4W Hi and pump. If the indicator lite goes on and the front wheels turn, the switch is bad....easy to replace with a deep socket
Guess you could actually drive it and apply the same test with a long vacuum test line from inside
I will try what you all suggest, starting with shinden's procedure. I do get the 4H light when I push the button, just the front end isn't "locking" in. I will have to put jumpers on the battery and start the engine and check for vacuum on the line and go from there.
I pulled the vacuum line from the actuator under the battery and started up the engine and I get no vacuum when switching from 4H to 2H. It must be the vacuum connection on the transfer case causing the problem. Is there a known point where these lines connect to the engine that could have gotten disconnected?
I found the problem. It was a loose vacuum line and it works perfectly now..just in time for another snow storm here in the midwest! Thank you all for your help.
hand-vacuum
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