Solved problem! Ok, been reading until my eyes were bleeding and my 4x4 problem sounded the same as all the others. Fluid on vac lines, etc. Here is how I fixed it. Step by step. Just to let you know, I am not a mechanic or have any clue at all of what I was doing.....

1. My transfer case spewed tranny fluid from fill plug. So I replaced output shaft seal. This was done at my buddies garage. He is a mechanic so he did it for me. This is the only step I could not do at home.

2. Replaced transfer case vacuum switch. Like 30 bucks and bolts in.

3. Replaced vac line from actuator to transfer case switch, and main vac line off manifold. The main "t" is drivers side under hood behind abs. Simple to see.

4. Replaced vacuum actuator under battery tray, and replaced cable running to diff. While I had the cable assembly off. 3 bolts, I grabbed the bolt thing that the cable pulls, and worked it like crazy. The kind of movement I do when the wife and kids are out of the house. The diff fluid was changed too, so all I did was work the "lock" inside.

5. Turned on, and bang, 4x4 again. The main problem was vacuum. Here is a simple test. Remove battery and tray to see actuator. Use jumper cables and get power. Fire it up and go to 4hi. You will see the actuator move, but use your fingers and try to push it in farther. You should feel a little grinding, and then it will lock. If that happens, work on vacuum ... I hope this helps someone. Mike

 

I have a 97 Jimmy, with a problem with sucking my tranny fluid dry, before I get into changing the front seal, I want to try the vacuum switch. I have a new one, took off teh case guard, but can't find it !! Please give me an idea where it is, left or right, top, where???
Many Thanks,
Mike

 

If you have an overfull condition in the transfer case, the vacuum switch will not fix it. You have a bad input seal.

 

I'll check the fluid level tomorrow, but wanted to put in the switch, I already had it, so it wouldn't hurt. I appreciate the pointer, very much. Any idea just where the switch is located? Right/left/top/side?
Many Thanks,
Mike

 

4WD oil in vacume tube?
Found using the search term "vacuum+switch+location" and author "swartlkk" both without quotes.

 

I have a 98 S-10 Blazer, Should the front shaft spin free, the one from the transfer case to the front diff when it is in 2 wheel drive, it is a three button. Sulley

 

If You have a "3 button "system, Your Blazer is NOT a constant all wheel drive, so the drive shaft to the differential in the front, should turn easely and is not "driven".
Engaging the front-wheel-drive, through the transfer-case,also blocks the front differential (with the famous vacu-module), through a vacu-swich on the transfer-case.

 

Thank you. Sulley

 

About 2 weeks ago I had a loud noise coming from the transfer case. I knew that my cable was trying to engage. I pulled the old transfer switch out and it was stuck in about 3/4 of the way. I bought a Dorman vacuum switch, and installed it. No 4wd! To make a long story short and spending 5 days 2 Dorman switches and one GM switch I found out the three prong hose cap for the switch leaked vacuum on all bit the original switch. I measured the diameter of the 3 prongs on the original and they were about .014" wider than the Dorman prongs and slightly wider than the GM. I fed the cap over the tranny so I could easilly check my switches without installing them. I used a hand held vacuum pump, actually my one person brake bleeder, located the vacuum line that feeds the switch and tried to pull a vacuum on each switch. I couldn't pull a vacuum on either Dorman, but could on the GM, but the GM wouldn't hold the vacuum. I then cut the lines from the cap, installed the switch and connected one 5/32" or 3/16" vacuum line to each prong on the switch, spliced them on their respective vacuum lines from the engine compartment and I now have 4wd!

Added note one Dorman leaked vacuum without actuating the switch, so always check the vacuum input prong to make sure you have a good switch.

 

so swartlkk, what kind of a long cleanup process are you talking about if it got into the hvac system?