2004 Chevrolet TrailBlazer - Transmission issues

I have a 2004 Chevy Trailblazer SUV, four wheel drive with about 68K miles. During the last few years it has not been driven very much and it has been stored in a garage most of these years. Recently I have noticed that when I drive it it does not want to shift into the proper gear. Let’s say I want to go about 60 MPH, the TACH revs up to 6000 RPM’s and it stays there for as long as I maintain that speed. I brought the SUV to a local mechanic and he checked the oil, which has never been changed, and took it for a test drive. Came back a few minutes later and basically told me that the vehicle needs a new transmission.
My questions to you are: Could there be something other that is creating this issue? Like a transmission pressure switch, faulty sensor switch, or the possibility that the solenoids are going bad within the transmision, or any other part that might need replacement? Could high altitude be a factor? The SUV is being stored and driven at about 9500 ft, of elevation ( CO ) and never tows anything.
Anyway, I would appreciate a response and your thoughts on this matter at your earliest convenience as to whether I need a new transmission or is there a more simpler, easier solution to repair rather than to replace it? Replacing it is not an option on a vehicle this old, even though it still has a lot of life left!

Thanks, in advance, very much for any advice you may provide on matter,

Assuming you are not low on fluid. The cheapest and easier thing to do first is to have the tranny fluid changed to see if it helps. if not then I would bring it to a reliable transmission shop to have it checked out. not a chain store.

Chevy Trailblazer Transmission Slipping → Diagnosis | Drivetrain Resource (700r4transmissionhq.com)

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3 things - why do you doubt the machanic ? - get a second opinion - as far as we know Ray does not post here .

Concur w/ WW above. Auto transmission require very internal high fluid pressures to produce the forces necessary to shift the planetary gears from 1 to 2 to 3 to 4 … etc. The pressure comes from an internal pump driven by the rotation of transmission final drive (i.e. proportional to the vehicle speed). This pumps the fluid at a pressure proportional to the vehicle speed throughout the innards of the transmission. The pressure is the primary input for which gear the transmission uses. Higher pressure means it shifts to higher gears. That fluid path contains a bevy of seals needed to hold the pressure. If those seals leak, the fluid just leaks back to the pump, and the pump isn’t able to deliver the needed pressure . New fluid has fresh seal conditioners, which will soften the seals and hopefully eliminate or at least reduce the leaks, buying you some time. If this is in fact the problem, the incontinent seals will eventually need to be replaced, meaning a transmission rebuild. Hopefully a dose of fresh transmission fluid will get you back on the road for some time at least.

I also have a 4WD truck w/automatic trans, and had the transmission completely rebuilt for this same reason, at about the 15 year old mark. In that case a dose of fresh fluid wasn’t enough to do the trick. Been working like new after the rebuild.

Note: If changing-out the transmission fluid on your particular transmission design is usually accompanied by replacing the transmission filter, be sure to do that too. And make sure the replacement fluid meets the manufacturer’s specs for your transmission. Might be a good idea to buy the fluid at a dealership, then you’ll know you are getting the right stuff. Best of luck.

BTW, common sense says to ask your shop to check for any transmission related diagnostic codes as the first step. I’m not Ray btw, just a driveway diyer. Ray doesn’t answer questions here directly. Ray however sometimes will answer a question posted here in his newspaper column. Or you can ask him directly, surf over to the Car Talk home page, right hand side of page says “Ask Ray”

Thank you for your input,I’ll try the new fluid

Thanks for your input,I’ll try the fluid change

I’ve owned three of these trucks, an '03, '05 and now an '08. My neighbor has an '05. The transmissions in these are pretty robust. I don’t hear of many issues on the chat boards for these either. Is this an issue that just cropped up or have you noticed it getting worse over time? Certainly, a fluid change is first step. Then I would do as advised by others, find a local, well known shop to get a second opinion.

If the battery went dead at any time, the transmission control module may require a reset.


Thanks for the information. I will rry it out!