My Blazer has been driving fine up until a few weeks ago. While making a quick run to town it starting driving weird while shifting. As I was driving it suddenly felt like it would not shift and the RPMs suddenly starting rising without much momentum. So I eased it back home. Once I got out I could see white smoke coming from under the truck, but did not see any leaks or anything. Prior to this I had the p1870 code come up on the truck, but it went away after unhooking the battery to do a radio swap. also prior to this I had been having RPM jumps of about 200 rpms while driving between 35-50 mph. I finally decided to take another look at it last night and drove it around the yard a few times. The truck does move but feels like it is dragging. The RPMs got up to around 4000 and the truck was only registering about 15-20 mph on the speedometer. I did not notice any smoking this time around. It feels as if the tranny is not engaging at all. The tranny has about 120k miles on it now. The filter and fluid have not been changed. I am trying to figure out if I need to change the fluid and replace the solenoids on the valve body or am I looking at a bigger problem? I have not tested the 4x4 to see if there is any difference there.