Transmission does not shift?

This was the problem on my transmission. I changed all solenoids and the transmission is working again!

I have a 2005 Chevrolet Trailblazer with the 6 cylinder engine and 4L60E tranny. On way home from a trip the transmission would not shift into 4th gear (overdrive). 1-3 gears shift fine. No engine codes being displayed. Changed fluid and found no metal. Took to a local transmission shop and they are stumped. Shop advised that when they hooked up to the computer they advised they can see where the computer is sending the command to shift into 4th gear, but it's not happening. He advised if it was a clutch pack problem it would "neutral" out when given the command to shift into 4th, but the truck just stays in 3rd. Tranny shop is leaning towards computer or electrical, but still unknown. Any ideas?

It's my understanding that on this model the shift solenoids are both activated in 2nd gear. If so doesn't this mean they are both good?

If they see that the computer is sending the signal to shift into 4th gear have they checked at the trans is the trans solenoid receiving that signal if so the would eliminate the wiring to the trans and at the trans what controls 4th.I would go more towards electrical but poss. Internal trans problem. I will look up the control circuit and see what controls 4th. And will get back to you.

That would be a great help. Thank you

There is a TSB for your car but it doesn't help our situation
Ref num 00-07-30-022D
Affected models 1993-2005 GM Passenger cars and light duty trucks
no rev, second gear or fourth gear
replace reaction sun shell with more robust heat treated parts

I thought about that but if the sun shell busted I would have metal in the pan but it was clean. Thinking about bringing it home from the tranny shop and taking a look at the wiring. How would I test to see if the transmission is getting the shift command from the computer. Do I need the Tech 2 for that?

Yes you need it to accurate the sensors and see what is going on. That why you can actuate that sensor and check it see if in specs also you can check the pressures in the valve body so you can see if it is electrical or pressure problem.

Removed transmission and had it rebuilt about two years ago. Never an issue but lately I have noticed that when it is cold, when first started up and placed in drive, it will change gears from low to second and will not shift on up through the gears into third and so on. After a couple or so miles when engine is good and warmed up, then it will change flawlessly in any gear. There is never any slipping. I thought maybe transmission filter so I bought that and the fluid required and put that in myself. It seemed to make really no difference. I did not notice any metal whatsoever in the pan. Beautifully clean. I am at a loss. Can anyone offer any advise? Governor pressure solenoid?

I appreciate all of your help. It did end up being an internal problem and the transmission was rebuilt. Thanks again

It starts and runs but when I drive it it shifts the first two gears but when it will not shift into third. I was told this might a PCM problem. I also checked the fluid it is not low. I just want to know for sure so I can get it fixed. Thanks

That is a good place to start. Thanks.

I have a 2004 Chevy Trailblazer 4 wheel drive w/ 98,000. I had a problem with it when I go to take off, around 20 mph, my RPM's goes up real high to about 4, but my car doesn't seem to want to go. But it will eventually shift into gear at the 30 mph mark. It's like it won't shift into that first gear. Other than that it runs great. And I noticed that if I slowly take off and let my foot off the break it will shift and the RPM's don't go high. I had a mechanic use a hand held computer device to check the tranmission and he didn't see anything. He also put a transmission filter in. Could this be my transmission or something to do with the 4 wheel drive switch?

Have you ever received an answer to your question? I have 2004 Trailblazer with exactly the same issue you described. Please reply if you found (or didn;t) a solution.

Ok. Check engine light is not on but I will have it checked and respond back asap.