I just bought a 1990 seville with 150k miles. I drove it for 20 minutes and it ran fine, then the transmission lost 3rd and fourth gear. it shifts out of second, but then it doesn't hook up in third and the motor revs freely.

There is a vacuum line hanging down on the passenger side in front of the front wheel I can't figure out where it goes. the trans fluid is full.

ANY ideas on what might cause this? I really need to figure it out, I don't have any car to drive.

Have you tried to manually shift the car?

Also, could you be more specific about the vaccum line? Try this: see where the vaccum line comes from (throttle body (TB) perhaps). Look at your emissions tag and see if you cannot match the hose routing to something similar on the TB. Once done, you should be able to tell where it goes. I doubt however that it goes to the transmission (vaccum modulator).

I have looked at the vacuum hose, but can't figure out where it ends up. It got dark as I was beginning to figure it out.

Have you guys heard of anything like this happening before? What was the cure? Thanks

your trans is in limp mode pobably i had the same prob and had to get a rebuild on it and drove 300 miles and now the same thing she's going back to ammco for round two

I have looked at the vacuum hose, but can't figure out where it ends up. It got dark as I was beginning to figure it out.

Have you guys heard of anything like this happening before? What was the cure? Thanks

Try dropping the pan to see what's at the bottom of it. If it's full of clutch material, it is probably due for a rebuild. If the tranny has not been rebuilt after 150k it is due or getting close for it to be done. Also install a new filter and see if it helps.