The Ford 10R80 family of transmissions has become known for the CDF clutch cylinder sleeve moving out of position. An updated drum has been made available by Ford with a “no-walk” backing lip to prevent repeat failure. After this cylinder has been replaced, there still may be another problem still lurking in the transmission that may get past you. It is not a common problem, but when it is a problem, you will need to get a 10R80 shaft.
The input shaft in this transmission is about two feet in length. It has many different pressures going through this shaft as Figure 1, above, shows.
The area of concern is related to the converter, C, D and F clutch circuits. Looking at Figure 1, the C, D and F circuits are fed at the front half of the shaft and exits out of the back half of the shaft. The rings on the back half of this shaft seal inside the sun gear shaft (Figure 2).
The sun gear shaft has outer rings on it (Figure 3), which seal against the sleeve that is known to move out of position inside the CDF cylinder (Figure 4). This makes air checking these three clutch circuits through case passages very difficult (Figure 5).
Air has got to go through the stator support into the input shaft. It then exits the input shift passing through the sun gear shaft and into the CDF clutch cylinder. But, when attempting to apply these clutches, other than the converter clutch passage, no air should come out of the tip of the input shaft (Figure 6).
If air does come out the front when checking the C, D or F clutch, a cup plug inside the shaft has blown out. When inspecting this shaft, a cup plug should be seen blocking the passages to the tip of the input shaft (Figure 7).
If it is missing, damage to the converter and the clutch will occur quickly. A coat hanger can be used to verify if the cup plugs are present or not (Figure 8). Figures 9 and 10 reveal the D Clutch cup plug is missing.
If this occurs with your 10R80, damage to the C, D and/or F clutch should be observed along with an overheated converter. A repair of the shaft would require the right size cup plug and a long enough punch to set it in place. Otherwise, you will need to get a 10R80 shaft having gotten the shaft.