Posted on Pontiac Forum, but would like to run it by the Reatta Folks too as it is the same setup:

Here's the problem: 1990 Bonne SE, Has good reverse, but no forward gears at all. The shifter arm on the tranny is moving properly when moving the shift lever thru the gears. For the last few days, when shifting into drive on a cold/cool engine, there has sometimes been a buzzing or whining noise for a second or two, but the noise would quit and car would operate as normal. Today, wife went shopping, 3 or 4 mile round trip. All was fine 'till she stopped for a traffic light 1/4 mile from home (on the return trip). When she accelerated from light, the noise occurred, then about 100 yards from home all forward gears stopped working, no noise at all. Fluid is full, does not smell burnt.
Any suggestions on what I might check before going to a tranny $$$hop? Appreciate any help,.... Jim

Sounds like it's going to take more than Seafoam. You should pull the pan and check for shavings. Run a clean magnet through the oil. Also look for copper that won't get picked up by the magnet. If there's no shavings it will give you some bargaining power so you're not completely at the mercy of those gangsters. Steak

It seems unlikely but the shifter cable may have popped off the trans.
The other possibility is the cable is out of alignment.
It sound like it is moving out of gear and into neutral.
Try shifting to 1st gear, you may winde up in 3rd or 2nd.

My car had trouble in any gear afater it warmed up. I changed filter and fluid and for 500 miles no problem. I took it to Aamco for a total fluid flush. They told me it was a bad converter. They quoated me 1200 for a complete rebuild which I reluctantly allowed. Then when I picked it up they made me pay $1967 today. I am not a happy camper right now! Particularly knowing I have three good trannys laying in my garage!

aamco are thieves, Never go there, they always say transmission needs rebuilding and quote a price. then charge more , I had this happen to me, then talking to a friend, they did it to him.

Aamco should be blackballed, How do we do that?