4F27E变速箱维修手册

TRANSMISSION THERAPYFamiliar Failures andFaithful Fixes for theby Larry FrashMazda FN4A-EL and Ford 4F27Ehe FN4A-EL/4F27E was firstintroduced in the 1999 MazdaAlways check thisProtege.These transmissionsbushing for wearare used in a variety of Mazdas,andin the Ford Focus.Overall,this hasbeen a fairly dependable unit,andis reasonably easy to rebuild whenit does wear out.But ever since thefirst one rolled off the assembly line,these transmissions have continued toexperience a few common problems.In this edition of Transmission Therapywe'll cover three of the most commonwear problems known to cause majorfailures in these transmissions.Stator Support BushingWorn stator support bushings allow converter apply pressure to cross leakWearinto the release circuit causing lockup slippageThe stator support bushingssupportthe turbine shaft(figures 1 and 2),butFigure 1they also separate the TCC apply andrelease pressures.With lockup released,converter charge pressure is deliveredbetween the converter clutch and theAlways check this.apply surface (the front converterbushing for wearcover).This hydraulic pressure is calledconverter release pressure,and thatpressure is what keeps the converterclutch from applying.When conditions are right forlockup to apply,the converter releasepressure is exhausted.Converter clutchapply pressure is always applied to theback of the torque converter clutch:theonly thing that keeps it from applyingis the release pressure.Once the releasepressure exhausts,converter clutchapply pressure is able to apply theconverter clutch.When the stator support bushingsWorn stator support bushings allow converter apply pressure to cross leakare worn,they can allow converterinto the release circuit causing lockup slippageapply pressure to leak into the releaseFigure 2side of the converter.When this occurs,8GEARS January /February 2006