I've got a 1995 Buick Riviera, Supercharged 3.8L series I. The transmission is failing, I believe.

I've lost the use of reverse and overdrive.

I believe I do have 1-2-3 gears, though only when the engine light comes on. Generally the light comes up when I start the car, stays on for a few seconds and then goes back off. I've got to rev up the engine for no more than a minute (with a few exceptions) to get it to come back on, and then the car will pull away again.

This all seemed very convicting, though the other day when I was fighting my way to a store, the light went off and instead of the usual loss of drive, it shifted into OD, cruise worked, and the car felt like it used to. That lasted for most of the drive, though when I stopped to turn onto my street, I lost my movement, and it took awhile to get it back.

I've checked the tranny fluid, and ran an OBD reader on it when the light was on. It claimed that I had a failed speed sensor, though my speedometer hasn't acted up in the least. I'd like to think its something simple, a loose plug, for example, though I can't seem to find anything that appears awry.

The trans is specific to the 95 year and supercharged edition, though I can't imagine that its much different than any other 4T60E transmission, have any of you experienced this downer?

Try changing the transmission fluid and filter. Sounds to me that the filter may be plugged up and not circulating the fluid properly. If that doesnt work then change the sensor mentioned.