Pawl

At speeds of 50 mph and up on the freeway the RPM guage is jumping around with a little bit of jerking of the transmission <---(I think). I bought a used solenoid from an auto wrecker last February and it seemed to work okay. Do I just test it with the 12 volt battery and if the solenoid is not clicking then I know what the problem is. Although it might test fine and be faulty when driving. This car has 160,000 miles and I am wondering if I just need to buy new ones and get it over with.Maybe the bottom one is bad and I just need to change it. I will test them both tomorrow. I have an identical Honda here that runs fine.I can switch them with this car. Any hints or sugeestions? Thanks Paul