Does your FMX have a strong reverse? If so you probable do not need a rebuild. Problems with the vacuum modulator, detent lever (kickdown) or a problem with the release circuit of the intermediate (2nd or front) band servo will cause delayed or no shift into 3rd. To shift from 2nd to 3rd the FMX...
I was in the transmission rebuild business for over 30 years. I owned 2 shop locations with 20 employees at one time. I would strongly recommend that you pay the extra $800 to have the entire job done professionally. Almost all the problems I saw over the years with transmissions after a DIY...
