1998 Mazda protege overdrive messing up?

You need to find out what DTC is in the vehicle's PCM(computer). The transmission is a CD4E(I know this because I have a 626 with the same transmission-that I personally rebuilt.). More than likely if jerking exists it could be a faulty VSS(vehicle speed sensor - it fails to respond correct information to the PCM.The PCM does not know what gear to command the transmission into. ).You need to find out what DTC exists to accurately repair it. Once you find a DTC go onto the internet and look up this DTC and find out what other people did to correct this issue.