Transmission won't shift... Revs high!

My car wont shift gears, it revs up very high almost as if it were in neutral.
The car's trans was rebuilt about 40k ago.
Fluid has not been changed since then neither has the filter!
Today i checked the fluid and filled it up but it made little to no improvement.
Any suggestion will be appreciated!
I know im going to have to change the fluid and filter tomm but please enlighten me about wether that could be that cause or not, and if there could be any sensors that control this... Or if you guys think my trans is dead?

Who rebuilt the trans and what exactly did the construe as a "rebuild"? What was the warrenty coverage?

It was rebuilt 3 yrs ago and it had a 2 yr warranty. So it has no warranty.
But that is all pointless... I need to know if these are common problems or symptoms of WHAT?
Can it be something electrical??? Sensor or something... Any help would be appreciated... If i take it to a mechanic their going to charge me for a rebuilt when it could probably be something stupid.
Please Help!!!

But that is all pointless...

Not neccessarily. It helps us to help you by knowing what has been covered and what was replaced. If the trans was completley abused prior to the rebuild, some debris could have ptentially been left behind, or if the troque converter was not replaced, alot of possibilites are out there.

Another good chance here is most of the time after a overhaul, they want the fluid changed in 15 - 20K miles. Was this done? What is the current fluid condition (color & smell)?

Yeah that fluid has not been changed and it has been 40k miles

By the way don't trannys usually take a while to brake down?
My ex had a VW and the transmission was messed up for about a year and ahalf before it died. My car was working just fine a few days ago... Is it possible that it could get so messed up in just a few days?

Well, usually an abrupt failure as such would be loss the of the vacuum modulator or throttle valve cable out of adjustment.

did you notice anything before it stopped working? anything odd?

ok that sounsd good exepct i dont know were any of that is... can i change those things or are they IN the tranny. Can running the computer scanner detect those problems???

no nothing odd... by the way i took it to a mechanic today and he drove it one block and told me he was 100% sure that was the tranny.
Im going to try to get one from a junk yard so if anyone has had any experience installing and removing one of these monsters please share...

}he was 100% sure that was the tranny

Your 4L60E transmission is comprised of about 160 parts. One of them may have failed, and saying "It's the tranny" really doesn't help - You already knew that.

It may be as little as a clogged filter or filter fallen out of the pump. It may be as much as a pump or converter failure, damaged spline on an input or output shaft. It may be a pressure control solenoid, or even and electrical connector outside the transmission. Without a diagnosis beyond driving it, it would be very difficult to determine.

Does the DRIVE range engage firmly?
Does reverse engage firmly?
Does the transmission operate normally if you manually shift through the ranges?
Are there any trouble codes stored in the PCM? The '94 versions are the OBD "1½" type which have some enhanced capability, and may be helpful in diagnosing any problems.

Transmisison removal from a fourth-gen F-Body is not a lot of fun. Installation is even less humorous, but it's not as bad as some. Changing it unnecessarily is even less fun.

Before changing it out, it may be worthwhile to check the line pressure. Screwing in an external hose for a gauge is a lot easier than pulling the trans. Beyond that, there is quite a lot which can be done to the transmission without removing it from the vehicle. A multimeter would also be a good diagnostic tool for checking solenoids and the pressure and temperature sensors.