Chevy & GMC Vans

I am getting a clunking and shudder when slowing and stopping. It also does it occasionally when accelerating but goes away when it shifts into higher gears. Feels like rear end however I was told it is probably coming from my transfer case. Probably the viscous clutch. Any imput on this.

First, are all 4 tire exactly alike: size, manufacturer, type, pressure?

Mismatched tires will wreak havoc on an AWD, eventually destroying the T-case and front diff, and can cause similar symptoms like you describe.

What year Astro? If it is a 1999 - 2005, flush the transfer case with GM Auto Trak 2 fluid.

Thanks, I flushed it once because the local idiot put regular fluid in it and shortly after that the problem started. I flushed it about 20,000 miles ago but will do it again and again. This time myself in my garage with my tools on my time. Big box oil change establishments aren't the place to go I guess.