My 2003 Chevy S-10 (4.3L 4WD) shifts into neutral sometimes when going downhill if I take my foot off the gas. It then makes a noise like a playing card in a bicycle wheel. It's been doing this for about 3 years. I've spent a small amount of money to fix it. It has 95,000 miles on it. I had the 100,000 mile transmission service done early, but no change.

The RPMs go to around 1,000 on the tach. Pressing the gas, there is no engaging noise, it just proceeds normally.

I'm in "wait 'til it breaks" mode, but I sometimes worry it's going to leave me stranded in the boonies were I hunt.

 

Sounds like a broken mount or shift linkage out of adjustment.