A thud and then 2wd

[redfury]

Yay! I lost 4wd. My van has a 4wd transfer case set up and the first time I used it this year, I heard a whine out of it and it wouldn't electrically shift into 2wd on the fly. Then it clunked out of it. The second time I used it, it came out on it's own with a big THUD and now it won't re-engage. It worked perfectly last year. Hmph. The only thing different is that I changed tires. I'm going to have to measure the circumference of them to see if I've got a problem there, but in the mean time, I need to figure out what exactly happened to the transfer case.

Since I've never dealt with anything AWD or 4WD, I'd appreciate any input or diagrams for the 4wd transfer case for a 98 GM driveline. My shop manual obviously only covers the AWD case.

[Heavyopp]

I know there's a common problem in the blazers. Its got to do with the solenoid and wiring harness for the transfer case.

I'm sure a google search will bring up the answer.

[redfury]

I started doing that shortly after posting since I wasn't getting a bevvy of replies. I'm going to get up under the van today and see exactly which transfer case I do have, and see if I have the vacuum lines hooked up and working properly. Since I recently got the P0171/74 codes on the van, there's a possibility that there's a vacuum leak down there and I never got proper engagement.