A general list of reasons that cause transmissions to overheat was presented in a previous article called “Transmission Overheat.” In it the comment was made that with variations between manufacturers along with transmissions having their own unique designs, it prevents an article from getting into the finer points of things. This short newsletter will hone in on a couple of overheat issues related to Ford transmissions.
Daryl Keels at Econo Transmissions in Wilmington, N.C., quickly realized that there was a bypass valve somewhere in the system stuck in a position where it was directing the fluid back to the transmission without it going through the cooler. This resulted in transmission fluid reaching operating temperatures of about 270 degrees.
These as well as some other Ford vehicles use a transmission cooler that is integrated with the A/C condenser (figure 1). Located at the lower driver side corner of this assembly where the cooler lines enter (figure 2) is where this thermal bypass valve is located (figures 3
To correct this condition will require replacing the A/C condenser and transmission cooler unit. This can be a costly repair, for any owner including municipalities.
As a result, some have rendered the bypass valve inoperative which will allow fluid to circulate through the cooler at all times. This is not a good option in colder climates due to the possibility of fluid jelling. This will prevent no cooler flow and if driven, would cause premature failure of the drivetrain due to lack of lubrication.
Insert the machined aluminum plug with the .700” end into the bypass valve housing (figure 7), then install the inner heavy spring next followed by the inner plug and retaining snap ring.
After Daryl made these modifications, the transmission
These are just two examples of getting into the finer points of the cause to overheat problems. In some future newsletters, we’ll get into other transmissions as well.
