Auto trans car has 80K miles; AT "slips" ( similar to a MT going out of gear ) and only sometimes - when peaking a steep but short driveway, and sudden stopping @ bottom of freeway offramp...also has a small "klunk" or "thud" feel in shift from 1 to 2...no increase of these problems since purchase @ 65K miles thank you Artie

The first thing to check is auto trans fluid levels, if you experienced a sudden failure, look for leaks where you park, should be obvious given the sudden failure. I had similar slow leak, then all of a sudden trans would not go into gear, just slipped, so does your engine rev up when you push on gas? Have you ever serviced trans., most believe manufacturers recommendation which often says lifetime, but never define whose lifetime. lol Crazy, I know, but having a BMW it says lifetime, but think about it, service is the highest income producer for dealers, so simply put, don't believe manufacturers, servicing auto trans. is essential if you like to keep your vehicles for more than 100K miles.

If auto trans, does it fail to downshift?

If tranny fluid is clear and at normal level, then the issue is with the transmission - it is getting ready to go sayonara.

Better get that fix before you get stranded.

try checking fluid level, could be bad governer, but more likley clutches or bands ,or drums try to go through gears manualy in these newer cars the valve body is all operated by computers,You will probably need to take it to have it pulled and rebuilt, i assume it has over 80k miles

check and replace filter and fluids just like oil it tends to burn up and blacking and needs to be changed and flushed checking your tranny fluid it should be a red color not a dark red or with a black tint

If the trans. hasn't been serviced every 30,000 miles and it has over 100,000 miles on it, it's problem is normal wear and tear. The only way to fix it right to rebuild it. You can add Lucas trans. additive to it. It worked miracles in my ford truck. Use two bottles.It will free up the valves and seals to buy you some time.

have you towed anything with your car could of blown a fuse from the auto box therefore not allowing you to shift out or into park happened to a friend of mine that fixed the problem, check your fuses?

neeed to get rebuilt trans no matter what goop you put the trans

I had the same problem in my 96 f-350. The transmission has slipped recording a slip code in the transmission. You can pull the codes and get it. I shifts into a safe mode that increases the pressure inside your transmission as part od a fail safe. Plain and simple, you have to have the tranny rebuilt.

This may be caused by fluid starvation from a plugged trans filter, also a shift solenoid inside the trans may be sticking, I would recommend u change the trans fluid and filter (required at 60,000 miles), also go to a Kragen auto or any chain parts store like it and ask to have a code test run on the powertrain control module , it is free.