tranny problem with 90 Bonneville with 3800 V-6

More than likely the left front wheel is just turning due to lack of rotational resistance. It is probably going to be a bit more severe than you think. First of all, is it low on fluid? What condition is the fluid in, is it burn't smelling or discolored, if so, the damage is probably done. You can pull the pan and check for debris(metal, clutch material), just to confirm a problem. You did not state how many miles are on it.

Sounds like the axle popped out of the trans differential side gears,

or maybe a broken axle shaft.

Hope this helps.

That greatly depends on what the OP meant in his description. It is normal for only one wheel to turn when the drive wheels are lifted off the ground. He does not state if he tried to block that wheel and if the other wheel then began to turn. From his description, I would not suspect a broken axle. I'd suspect tranny problems.

Car is not low on fluid, and it is not burnt. The car was not used heavily for years, and has less than 100K miles on it.

While in Drive and up on jack stands, the left wheel turns fine, and the right doesn't turn at all.

But on the ground, the car will move fine under its own power in REVERSE, but it will not move forward in DRIVE or any other forward gear.

I agree with the other poster who said it is an internal problem with the trans. BATauto.com has a forum specific to transmissions with some very knowledgeable transmission techs, most notably a poster who goes by "Transman" -- he helped me with mine. Also, I think you should avoid running the transmission with the wheels elevated as I think this can (in some cases) damage cv joints because of the severe angular flexion due to the wheels hanging way down while rapidly turning.

Do you understand differentials? Power goes to the wheel with the least resistance. Do you know that much?

I do know what a differential is.

Do you understand that if the car will back up in reverse, but not go forward in drive, it's likely not the differential?

B> >> While in Drive and up on jack stands, the left wheel turns fine, and the

It doesn't help - the car will go into reverse and both wheels will move, and the car will move backwards in reverse gear.

Did anyone read the whole posting - the car started up find and I backed it out of the driveway. It goes in reverse just fine.

It just won't move forward in drive.

Do you get it - the problem is > Sounds like the axle popped out of the trans differential side gears, >

That is pretty much what Bon-ne-ville was saying.

You've gotten other advise to have the tranny checked. Some of us have told you that it does not at all sound like an axle, or a differential problem, but a tranny problem. Do you get it - have your tranny checked.

Maybe only half (the front half) of the differential is shot because it backs up OK.

Yeah - I never thought of that...

No Bonneville was claiming that the differential was the problem, one wheel would spin and the other would not. BOth wheels turn when the car is in reverse and only one turns when the car is in ANY forward gear.

B>> I do know what a differential is.

I have a 1989 Olds Delta 88 Royale that my sister is driving.

She came home telling me that the turn signals don't work. I went out to see for myself, and sure enough, they don't work. Not only do they not flash, but they don't even just come on and stay on without flashing.

But the emergency flashers work just fine.

Could it be a fuse, or flasher or the relay?

Yes

No he wasn't. You did not understand his comment at all. What he was saying to you is that differentials work exactly as you describe.