Ford 8F24 mechanical diode failure - Transmission Digest

Ford 8F24 mechanical diode failure

Mechanical diode failure in automatic transmissions is not uncommon. As far back as the AODE/4R70 shops have seen this type of failure. In April 2022 an article was published in Transmission Digest called, “The ins and outs of the Hydraulic Selectable One-Way Clutch (SOWC).” This article provided photos of the type of damage this style diode is susceptible to in 9T50 and 8F35 transmissions.

There is also an “electrically controlled” SOWC which is used in Ford’s 8F24 transmission (Figure 1).

This electrically controlled SOWC is referred to as the “D” Clutch and is controlled by a D clutch solenoid. This means both electrical failures and a mechanically failed solenoid can be added to the list of reasons for problems.

This electrically controlled SOWC is used to lock the rotation of the input ring gear and reaction/overdrive planetary carrier. In Park and Neutral, the “D solenoid” is energized, which causes the SOWC to lock the reaction carrier from turning in both a clockwise and counterclockwise direction in anticipation of Reverse or First gear engagements. When the vehicle is in first, the solenoid will turn off. The design of the SOWC with the solenoid off allows the carrier to be held stationary in one direction but freewheel in the opposite direction. Only when in Manual Mode paddle shift first gear will solenoid D be turned back on to hold the carrier stationary in both directions, providing engine braking.

Recently, a 2020 Ford Escape using the 1.5L turbo engine came in to Transmission Masters with a No Reverse condition. P0766 for Shift Solenoid “D” Performance/Stuck Off was stored as well as P2703 Transmission Friction Element “D” Apply Time Range Performance. Both codes point to a problem with this electrical selectable one-way clutch assembly. Ford says that if either DTC P0766 or P0767 are set, resolve them first. Otherwise, for DTC P2703, you are sent to a symptom chart where it says that if the D clutch solenoid is mechanically stuck off, you should replace the assembly.

ATSG’s tech advisor Rino Partipilo provided Dave from Transmission Masters with a Ford bulletin about this concern. Bulletin number 21-2421 explains that some 2020 Escape vehicles equipped with front-wheel drive (FWD), a 1.5L EcoBoost engine and an 8F24 transmission may exhibit no reverse engagement with diagnostic trouble codes (DTCs) P0766 and P2703 stored in the powertrain control module (PCM). This may be due to small particles in the electronic SOWC, causing the internal lever of the electronic SOWC not to deploy correctly. Figures 2 and 3 show what the solenoid is supposed to do when it is energized.

Tech-Speak-April-Figure-2-600
Figure 2.
Tech-Speak-April-Figure-3-600
Figure 3.

To correct this condition, the electronic SOWC and fluid filter will need to be replaced. The part number for the electronic SOWC is J1KZ-7P030-C. A new one costs between $150 and $180 depending on where you shop. The filter (J1KZ-7G186-A) is about $15.

With Solenoid D being stuck off causing the No Reverse concern, if the vehicle is equipped with a Manual Mode using shift paddles, there will also be no engine braking in manual low, as the carrier will be allowed to overrun on a coast.

We thank Dave from Transmission Masters who provided these photos with a unit he was dealing with, making this article possible.

Read more stories from our Technically Speaking column series here.

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