Who does speedometer repair? Everything in it is fine but it reads slower than actual speed.

Are you sure you have the correct speedo gear in transmission base on rear end gear? If you have changed tire size from stock size this will also have an effect.

Yes, only had 26k miles, stock wheels and tires, unmolested original farm Jeep, new speedometer cable, speedometer reads 0 when doing 5-10, 20-30 when doing 50. This is a 1978 Jeep CJ5 and they were notorious for speedometer and gauge issues.

Old Mechanical speedometers have magnets in them. Over time they loose magnetism. The magnets need to be recharged then the strength adjusted / dialed in to the proper speed. My advice is to call around to speedometer repair shops for just this service. Should be cheep because they dont have to take apart and replace parts.

That's EXACTLY what he is asking for

Is the odometer accurate? If yes, then the speedometer needs remagnetized or just a simple clean and lube.

If the odometer is off too, you need to look at the drive gear ratio. Might be a small gearbox on the side of the transfer case.

https://www.bobsspeedometer.com/

never used them but its the only one i have heard of