93 Honda Accord

Is there such a thing as a “speed sensor” that might communicate with my transmission? My car downshifts too dramatically when I let off the gas. I have 84K original miles on the car.

Yes, there is a vehicle speed sensor (VSS). It’s mounted on the transmission.

Can it be replaced without taking the transmission apart?

Why change the VSS (vehicle speed sensor)? You won’t solve the problem by changing a lot of parts.
There are several sensors that the engine computer listens to which affect how the transmission shifts. Are you going to change them all?
Are there DTC codes? Does the check engine light (symbol) blink? For the automatic transmission, does the D4 light, on the dash, for gear shift position position blink?
When the two female terminal Service Check Connector is jumpered with a paper clip, and the ignition key turned ON, does the D4 light blink a code(s)? There are 15 DTCs for the transmission. Throubleshooting is the first place to start, NOT, with a wrench.
Actually, start with a transmission fluid change. It’ll take about 4 to 5 quarts. Then, if there is ANYTHING wrong with the engine performance (NOT high performance, just normal performance), repair that.
Test, check, the sensors to ensure that their output is nice and smooth, and gradual. Especially, check the Throttle Range Sensor (aka TPS) just off idle position. Check, both, ohms and volts.

You said you had an older Honda on another question that I posted. My actual concern is: “My car downshifts too dramatically when I let off the gas.” It has been suggested that it is a speed sensor issue. Does your Honda reduce its speed dramatically when you take your foot off the gas?

Does the D4 light blink a code 14, or 15 when the Service Check Connector is jumpered? If it does, alldata.com has check charts for that.

You don’t want to be bothered with troubleshooting. That would be nice if it were possible; but, it not often is possible. Besides, if the problem comes back, you’ll see that just changing a part wasn’t the answer. Then, you’ll ask yourself, “Now what?”.
There are TWO Speed Sensors, on the automatic transmission, on the Honda Accord. Ut oh! The NC Speed Sensor is one. It is involved with the operation of the transmission lock-up torque converter.
The NM Speed Sensor is involved with shifting. A defect here causes a, “hard jerk during shifting”.
Check (inspect) the wiring, on the automatic transmission for the NM Speed Sensor. Remove the NM speed sensor and remove any metal shavings (or, other debris) from its pick up. Put it back in, reset the engine computer codes (disconnect battery), and test drive the car. If there is still a problem, you can change the NM speed sensor; OR, do the test to see if it’s at fault.
Here is more information and the location of the two speed sensors: http://techauto.awardspace.com/transmission.html