trany problem, dealer warrranty ends soon!!

[rjones2001]

I recently bought a used 97 Chevy Lumina LS and have had a problem with tranny. Most days, tranny changes very well into 4 gears, but sometimes it will not change into 4 gear with the RPM's running near 3. Usually it runs at 2. Called the dealer, service recommended that it does this when engine is cold and also recommended me running it 15 minutes to see what happens. When it running 50 mph+ without shifting in last gear (4th) it runs hard, like is going 80+ The problem exists sometimes, but not always. Does anyone know what this is. Im under warrantly, but will run out soon.

[Crackerman]

Check the fluid level.. if that's not it, take it to the dealership(tow it if it is farther to drive than how many miles u have left on the warranty) and have them take care of it...that is, IF the tranny problems are covered in tha particular warranty u have.

[transman]

does your check engine light come on, when you notice no 4th gear change? and what size motor does your 97 lumina have?

[rjones2001]

no, the check engine light does not come on unless i started the car (you know all lights light up for bulb check); I have a 3.1 LITRE V6 MFI. I have changed the "jet black" transmission fluid considering its supposed to be pink and the dealer paid 50% of the bill since he felt sorry for me because the previous owner would come to his service dept for every maintence item. I spoke with another dealership and they recommend tranny fluid changed every 60K. considering mine had 61K with black fluid, that might be part of the problem. Also, since the tranny fluid has been changed, i only notice it stuck in fourth gear is when the car has been sitting in yard all night (after it warms up it ok) My uncle is a mechanic and said it was normal in his camaro Z28 when it was cold so Im hoping their is no more problems, but will keep you posted, any more advice? Thanks for your input transman

[Crackerman]

change the fluid again..the fresh stuff u just added cleaned out all of the old trash that was in there... if u change it again it will last much longer... also the black means something is burnt or slipping badly or contaminated, i would have it looked at soon, but if funds don't allow, i can see ur argument

[transman]

haven't been here in awhile busy doing more web sites and fixing crash.
had a 95 buick riveara just recently, doing the same thing, but the riveara would set a tcc slip code, this riv had a woven clutch in the torque convertor, "and the ability to trip the tcc code". (some vehicles do not trip this code) but anyhow after reaching operating temp, the car would loose 4th gear (and tcc apply) untill the key was turned on and off.
you mentioned your fluid was black, possible bad linning on tcc clutch, find out from your dealer if your car can set a "tcc slip code". i am at home do not have info before me sorry. but on the pass side axle area, towards back of case is a white tag, please give me the numbers off of that tag if dealer can not help you, if dealer does not help you i will also be asking for some numbers off of your tag in trunk