saubor

I've bought an used Challenger 1800 97, and it's working very well, except for two things:
1- the speedometer is not workink. I don't know if the problem is with the speedometer itself or with a cable.
2- as the Challenger has two motors, the RPM should match, but they are different. With the engine off, one is marking 500 RPM and the other 1.000 RMP. Can I fix this easily?
Thanks for any help.
Saulo