A friend of mine pointed me this way due to my current problems; I've been working on this for three weeks and am no closer to diagnosing the issue, so hopefully someone here can point me in the right direction.
As the title says, it's a 1997 Oldsmobile 88, 3800 Series II V6 engine, I think 4T60E automatic transmission. When all this started, there had been a blizzard; the car slid off the road into a ditch. This actually didn't do anything but some cosmetic damage, but due to the slick roads, it had to remain there overnight. The next day, a friend attempted to pull it out, which got it mostly out until it slid sideways into another ditch (this time not doing any damage). This ditch was considerably longer and had a shallower approach a few hundred feet up the road, so I drove towards that point until finding a patch of ice.
The following day, the ice had melted enough that I could get the car out of the ditch once and for all; however, beginning that day, I no longer had reverse. Additionally, whenever the car got above 20mph, a few seconds later the transmission would slip and not re-engage until dropping back below that speed. It was absolutely night and day between the two days' performances.
The TV cable seems to be functioning properly; all connectors to the TCC seem fine, and the PCM is producing absolutely no diagnostic codes and the MIL is not coming on, though it is confirmed working. Fluid levels are correct, and the fluid looks to be in excellent condition. I initially thought I'd heard a noise, like a mildly high-pitched sputtering timed with the engine's RPM, but I think that may have been present prior to this after having studied it at length. All associated fuses I could think of are fine; that includes 5C on the driver's side, 5 on the passenger's side, and I think one more on the driver's side. The vehicle engages in Drive and all three "manual" gears with no problems at all; the only issues come from Reverse and what I assume is automatic overdrive. This tells me that the issue is something to do with the "automatic" part, but I could very well be wrong.
I've had no end of electrical problems with this vehicle, so I would not be surprised if this is the problem here as well. The ditch had quite a lot of tall, tough grass, so I could also believe something got knocked loose (however, I cannot make heads or tails of the underside of the engine past the two pans). I cannot afford to take it to a mechanic, and even if I could, the closest is a good 20 miles away at the very least (I'm not 100% sure; they could just be a towing service). I have a very hard time believing it's something mechanical within the transmission itself, as there was absolutely no indication of any problem before this and the state changed after having sat doing nothing for a day in an entirely level position.
Any assistance at all would be greatly appreciated; I'm at my wit's end.