1993 Speedometer extremely over-indicating speed

Hello! I recently purchased a 1993 4runner 4WD V6 automatic and have been loving it so far, but after taking it on the first 100+ mile drive my speedometer has started acting up.

I was driving along the highway and looked down to see my speedometer had suddenly gone to 110 mph despite only going about 70 mph. I slowed down a slightly and the speed dropped down as I slowed down, but it was still way over what it should have been. I drove along for a few more miles and suddenly the speedometer flicked back to what I would expect the speed to be.

20 mins of highway driving later it suddenly went back to showing me at 110 when I was going about 70. And it hasn't gone back to normal since then.

The speedometer will rise and fall as I accelerate and deaccelerate and will go all the way down to 0 when I come to a complete stop. However, as I accelerate the needle will rise much faster than it should, showing 40 when I'm going less than 20 or show 80 when I'm going 50.

I crawled under the car and it appears to be a electronic speed sensor and not a mechanical cable. I'm thinking the fact that the speedometer is still moving means that its not something in the speed sensor or cables but perhaps the gears within the instrument cluster itself? Any advice on diagnosing this issue would be appreciated.

I also was planning to take a trip this weekend and I wanted to know if the speedometer could cause issues with the transmission or something else catastrophic. Or is my speedometer problem only an issue for staying under the speed limit?

Thanks

 

Doing some more research it looks like maybe there are two different speed sensors for my car (?)

A sensor, speedometer (83181-35051)

And a sensor, speed (89411-35010)

I'm guessing that the second sensor is used by the transmission and the first is used only for the speedometer? If that's true then does that mean that my speedometer issues will only affect my ability to gauge my speed and will not cause any other problems for me on my trip if I can't get this fixed before this weekend?

 

Just to let you know, mine did that many years ago. It finally gave out totally and wouldn't read at all. They changed one of the sensors but it didn't fix it. Turned out the cluster was bad.

 

Ugh, that's what I'm afraid of. It's going to be a lot more painful to replace the instrument cluster compared to the sensor.

Did the speedo issue ever cause any issues beyond being able to tell how fast you were going?

 

Nope. I just used the tach after it went out until I made it to the dealer.