I have a 2003 Trailblazer that is very loud when you first start out in cold weather. It seems to stay in low gear and rev way up for the first couple of hundred feet that you travel, then the engine idle goes back to normal, it shifts and returns to a normal sound. Last night I drove it about 8 miles and everything was normal. I parked it for about 20 minutes, when I returned home, it was making the high reving sound allthe way home. It seems to be shifting at normal rpms and has no trouble shifting. It does get more quiet in high gear. I just replaced the trans lines and the fluid is normal, the 02 sensor was also replaced as well as fuel sending unit and fuel lines. Any help would be appreciated.

 

I checked it out again today, I think that the trans isn't engauging correctly. The engine is reving, but the trans is slow to shift to the next gear. It does seem to be shifting at the correct rpm's, but I don't think they are accurate, the engine sounds like it's at a higher rpm than the tach is reading.

 

In checking with other forums, I've concluded that it is the fan clutch that has gone bad. It seems to be a very common problem with tb's, good thing I bought the extended warranty.

 

Had the same problem with my '03 Trailblazer. Not surprising since I've had problems since the day I bought it new. I too purchased an extended warranty and I'm glad I did.