Well what can I say... I have had a 2001 STS for three years now, bought it used and now have around a 125K on it. I keep this car meticulously clean and do a lot of repairs myself. To date, I have repaired a vacuum leak, replaced the air compressor and evaporator tube, new tires, brakes etc... All in all, I love this car. I still am dumping in extra oil, about a quart every thousand miles or so and I think my tranny is leaking... but I'm not sure where. I plan to do a transmission service next at a local garage but I'm really scared. I'm afraid that if I open the bottom cover it will never be same. Transmissions really scare me. Any advice?
If I was you, I would get a rebuilt one, not even mess with the one you have in the car. Come on, 125k miles is time for a major overhaul.
I purchased a 2001 STS Seville three months ago for 8K dollars. It looked like a new car. It had 89K miles on it, new tires, new front end work, new brakes, and tinted windows.
Six weeks later I replaced the transmission. Apparently the fourth gear was going out. I should have checked the tranny fluid prior to buying the car, but didn't because the dipstick was under some plastic part, and the message center said 99% transmission fluid. So, I figured it was just serviced and all was well. The salesman at the dealership told me it was just serviced before I purchased the car. He lied. My options were to have this tranny rebuilt by the dealership, which would only change out what they considered worn or not working parts. It cost 3K dollars with a one year guaranty. Or a complete GM rebuilt with a 3 year/100K guarantee for $4,700. I went with the GM rebuilt for $3,700 and I used my own mechanic. Dealing with dealerships make me nervous.
Now I'm dealing with a one quart of oil usage every 1K miles issue. I went on line and found out that GM recommends a decarbonization procedure done chemically, and one person wrote that after the procedure he hasn't burned any oil between changes for 40K miles.
Wish me luck.