So I'm having issues with the transmission in my 2002 trailblazer. The transmission was rebuilt at 135,000. I'm up to about 170,000 miles now. I was intermittently losing 2nd and 4th gear, so we replaced the solenoid, but that didn't seem to fix the issue. Around 40-45mph, the truck cannot determine what gear it wants to be in so it will fluctuate between 3rd and 4th causing a surging of RPMs. It seems to be an electrical/solenoid/computer issue. I will be the first to admit that this is not my strong point. I love my truck and just want to get it back to where it was when I bought it.