My speedometer is erratic

Most likely:

1) Loose wire
2) Speed Cluster
3) speed sensor

You could have a bad speed sensor you have a check engine light on get it scan and most likely you gonna have a bad speed sensor

Scan the system for fault codes, you could have a defective speed sensor or a defective speedo both are possible.

Your problems sound like they are electrical, i would suggest you take it to an electrician and have them identify the problem, it most likely is not the speedometer as all that does is just output the speed, the speed sensor might be one thing you can look at.

This is your speed sensor. Now i do not know if this is going to be cable driven or electrical because they used both in 95. Your local auto parts store will tell you exactly what kind is in your truck. I just changed one friday on a 94 ford escort and it was electrical. The part was around 20 dollars for the speed sensor.

sounds like a bad speedo drive gear or speed sensor mounted on the rear of the trans there is no speedo cable, its electronic its not expensive take it to the dealer they will know exactly whats wrong with it

Although you didn't mention it, the speedometer probably bounces also. Replacing the speed sensor on the side of the transmission should solve both your problems. Good luck

I don't know what is causing this problem, but I know phil140701's answer is completely wrong on two counts. First, 740 Volvos starting at least in 1986 have electronic speedometers and no cable. There is an electronic sensor on the differential which sends a signal to the speedometer cluster. Second, if it were strictly mechanical with a cable then the voltage regulator could have no effect on it at all.

I have a similar issue, although mine do not stay off. Occasionally, my entire head just resets. RPMs go to 0, speed goes to 0 and the clock resets along with the trip.