The other day I was drive home from work when my 92 ssei with 254,000 miles shifted out of overdrive and into drive all by itself!!! I don't think the tranny is going out because it still has alot of pull, there is no slip at all. Sometimes it will shift back and other times u have to come to a complete stop and then go. Can this be a computer problem?

When is the last time you changed the fluid and filter?

I have owned the car about a year and a half. The fliud has always looked and smelled clean?

Take a look at this and see if it helps at all.

https://www.gmforum.com/t279318/

Thanks for the help.

I found the problem, it was a bad vaccum line from the top of the supercharger to a valve like canister on the frontend side of the transmission. Replaced the line and the trans. is shifting fine. I got lucky it was about a 3.00 fix.

Those are the best kinds of fix.

This true! I got really lucky.

NICE!!! i was having this problem also, fixed now though, thanks!!