While driving down the road, the speedo will drop to "0", then jump back to correct reading. Then will continue to jump down and back up. No error messages appear.

What's the problem and how do I fix it?

 

Do any of your transmission lights (D, D3, P, R, etc.) blink? On the 2G legend, there was a speed sensor in the transmission that would go out and D3 would blink.

In any case, you probably need a new speed sensor. I don't know where that is on the RL tho.

 

Check out the Gauges.pdf in the service manual here. There is a way to run a self-diagnostic check on the Guage Control Module at the bottom of page 2.

 

both speed sensors have been replaced, and problem has gone away.

Thanks, guys.