I have a 89 Ford Escort LX 1.9 and car just quit shifting out of low. Car was driving fine just all of sudden going down road and in Drive got up to 25 -30 miles an hour and it just reved up.I have checked and adjusted all the linkages,changed Trans fluid and filter,changed throttle position sensor,still no luck.Trans is not slipping,will go into reverse and drive etc.Does not have a modulator valve.Any ideas, would greatly appreciate any advice!