Welcome back to another issue of Keep Those Trannys Rolling. In this issue, we will look at a 2021 Ford F450 Super Duty truck equipped with a 7.3L engine and a 10R140 transmission from a local dealership. According to the dealership, the customer was experiencing a “slip on acceleration at times” concern. The dealership diagnosed the problem as a faulty valve body and wanted us to install a new one on the vehicle.
The vehicle arrived at our shop the following day with a new-boxed valve body on the passenger seat. As we all know, relying on someone else’s diagnosis is never a good idea. So, we started by checking the fluid levels. We found the transmission fluid was full but discolored. Next, we checked for codes in all modules. There were no codes listed in any module. We performed a quick visual inspection and then went for a short test drive to see if we could duplicate the customer’s concern.
DUPLICATE TO DIAGNOSE
During the test drive, we monitored the transmission operation. The transmission seemed to be working perfectly. However, as the transmission warmed up, we noticed the transmission would slip during the 2-3 shift under medium acceleration. As we continued driving, the transmission began slipping in 2nd, 3rd, 4th, 5th, 7th, 9th & 10th gears under medium to heavy throttle. With the slip concern duplicated, it was time to head back to the shop and diagnose this concern.
BACK AT THE SHOP
After duplicating the slip concern, it was time to diagnose this concern. We rechecked the computer system for codes. We found several ratio codes in the Powertrain Control Module (PCM). No other codes were set in any other modules. We connected a pressure gauge to the transmission pressure tap to check line pressure. With our scan tool, we commanded line pressure up and down and compared the pressure on the gauge to the desired pressure on the scan tool. The pressure was responding as commanded. With the pressure gauge connected, we headed out for another test drive. We monitored the line pressure while the transmission was slipping. The line pressure rose as commanded during the shifts. This indicated that the pressure control system could produce the pressure needed to apply the clutches. With the pressure control system working correctly, it was time to head back to the shop and drop the transmission pan for inspection.
TRANSMISSION INSPECTION
With the vehicle raised on the rack, we removed the transmission pan for inspection. During the pan removal, we found the fluid was discolored, and clutch material was floating around. With clutch material floating around in the fluid, it was obvious that a valve body replacement would not fix this transmission’s concerns. It was time to remove, disassemble and inspect this transmission.
REMOVE, DISASSEMBLE & INSPECT
With the dealership’s permission, we removed the transmission and disassembled it for inspection. During the disassembly, we removed the valve body and air-checked each clutch through the case. Each clutch air checked with 35 psi of regulated air pressure. Then, we continued to disassemble the transmission. Everything seemed to be okay during the disassembly until we removed the CDF combination clutch hub. The CDF combination clutch hub contains the C clutch, D clutch & F clutch components. During the disassembly of the CDF combination clutch hub, we found the C clutch frictions showing signs of slippage. We air-checked the C clutch circuit in the CDF combination clutch hub, and the C clutch seemed to air-check okay, but the piston was slow to move. With a slow-moving C clutch piston, it was time to take a closer look at the CDF combination clutch hub, C clutch drum, and piston.
TAKING A CLOSER LOOK
With the CDF combination clutch hub disassembled on the bench, we inspected the C clutch drum, and everything seemed okay. Next, we inspected the CDF combination clutch hub for wear. During the CDF combination clutch hub inspection, we found the combination clutch hub inner sleeve had moved out of position, partially blocking the C clutch feed passages (figure 1). With the C clutch feed passages partially blocked, it was apparent why the C clutch was slipping. With the CDF combination clutch hub sleeve out of position, the only fix was to replace the CDF combination clutch hub assembly. We contacted the dealership parts department and special ordered a new CDF combination clutch hub assembly and waited for it to arrive.
CDF COMBINATION CLUTCH HUB ARRIVES
A couple of days later, our new CDF combination clutch hub assembly arrived at the shop. We inspected the new CDF combination clutch hub assembly and compared it to the original CDF combination clutch hub assembly. During the comparison, we noticed that the new CDF combination clutch hub assembly was different. The new CDF combination clutch hub assembly had a lip machined into the hub assembly to prevent the sleeve from moving out of position (figures 2 & 3). With the new and improved CDF combination clutch hub assembly in hand, we started reassembling the transmission.
REASSEMBLING THE TRANSMISSION
During the transmission reassembly, we air-checked each clutch circuit at low pressure with 35psi of regulated air pressure. Each clutch circuit air checked properly. Next, we installed the new valve body per the dealership’s request. Then, we installed the transmission assembly and performed the Solenoid Strategy Download and the Adaptive Learning Drive Cycle procedures. Finally, we were ready for our final test drive.
FINAL TEST DRIVE
Before our final test drive, we rechecked all the fluid levels and checked the computer systems for codes. The fluid levels were up to their proper levels, and there were no codes in any module. It was time to head out for our final test drive. We headed out for our final test drive with our scan tool connected to the Data Link Connector (DLC). The truck seemed to drive pretty well. At first, the shifts were a little aggressive, but as the test drive progressed, the shifts settled down, and the transmission seemed to shift correctly. We continued to drive the vehicle several times, and the transmission worked perfectly. We notified the dealership that the vehicle was ready to be picked up.
Well, there you have it. By replacing the CDF combination clutch hub assembly, we were able to repair a 10r140 with a “slip on the go” concern. With a little bit of insight and a lot of patience, you, too, should have no problem “Keeping Those 10R140’s Rolling” down the road.
(Special thanks to Felipe and Art at Miramar Transmissions, San Diego, CA, for contributing to this article).
