10R80 aches and pains: Unintentional park hold - Transmission Digest

10R80 aches and pains: Unintentional park hold

The Ford 10R80 is a unit that visits specialty repair shops on a frequent basis with a variety of aches and pains. The automatic transmission specialist has diagnosed various symptoms that have become common ailments with these transmissions. The CDF cylinder sleeve moving out of position is one of these disorders (see Figure 1, above). 

The incidental contact of the P3 sun gear rubbing against the carrier spreading metal throughout the unit is another (see Figure 2). 

Figure 2.
Figure 2.

The aluminum drive shell or clutch cylinder, which has been affectionately nicknamed “the trash can,” is another area prone to illness. The external lugs on the F clutch steel plates are known to dig into this aluminum drive shell, compromising the application and release of the clutch (Figure 3). 

Figure 3.
Figure 3.

This would affect Reverse engagement and disengagement as well as the 3-4, 4-3 shift. With skip shift capabilities, this could mean a 3-5, 5-3 shift issue or a 2-4, 4-2 shift issue.  

Dave from Cain’s Transmission sent in pictures showing us another wear area of this aluminum clutch cylinder. It is where the P1 carrier sits as well as the low one-way clutch and B clutch hub (seen in Figures 4 and 5).

Figure 4.
Figure 4.
Figure 5.
Figure 5.

When this assembly is removed, a close look at where it lugs to the cylinder reveals the damage that can occur in this location (Figure 6). 

Figure 6.
Figure 6.

This allows the bottom side of the P1 carrier (Figure 7) to drop and rub against the P2 carrier (Figures 8 and 9). This will also cause metal to spread like the incidental contact of the P3 planet. 

Figure 7.
Figure 7.
Figure 8.
Figure 8.
Figure 9.
Figure 9.

Working with Jon from Bell Transmissions, another ailment was discovered. The symptom of this condition occurred in a 2020 Ford F-150. The vehicle was hauled in. The tow driver said that the service release lever did not free the drivetrain, so he had to pull drag the truck onto the bed. Jon had the drive shaft removed which enabled them to push the truck into the bay. This let them know there was nothing wrong with the rear differential. 

With the vehicle in the air, Jon pulled the release lever by hand manually, while another tech tried spinning the output shift using the drive shaft. They confirmed that the geartrain was locked. 

When he pulled the pan for a visual inspection, there was metal in it but no signs of a catastrophic failure. He inspected the park-rod which didn’t seem to move correctly. The tension spring was overextended like as if a roll pin that retains the bullet end of the rod had sheared. This prompted him to pull the rod assembly out for inspection. Once it was removed, the cause of this ailment was discovered. 

Rather than using a role pin as other park rods have, a tube spacer is used to position the bullet in the right location as park is selected and the bullet engages the park pawl. If the pawl hits the top of the park gear lug, the bullet compresses against the spring until the vehicle rolls enough to allow park pawl to drop into the gear between the lugs. The spring is used to push the bullet into place, locking the vehicle into Park. 

The problem, as you can see looking at Figures 10 and 11, is that the tube spacer split. The spring was then overextended, keeping the bullet in the park position and causing the unintentional park hold symptom.

Figure 10.
Figure 10.
Figure 11.
Figure 11.

The next step was to remove the transmission to see if the park pawl and gear were compromised before anyone could be certain of a full cure. And the question one might like to ask the owner would be, “Did anyone select park while moving?”

Read more stories from our Technically Speaking column series here.

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