Troubleshooting Pressure Loss in 10-Speed Clutch Packs

Since late 2017, we all have been dreading the day we would see our first 10-speed transmission come through the door. These units can look intimidating on paper, but once we roll up our sleeves and dive into these transmissions and look at how they function, they are no different than any other unit that comes across the bench. With six clutch packs and four planetaries, 10-speeds create a wide range of ratios, which makes them extremely versatile and allows this transmission family to be compatible with many platforms. 10-speed transmissions are known by a variety of names: Ford 10R60, 10R80, 10R140, the GM Gen. 1 and 2 10L60, 10L80, 10L90 and the Allison^® 10L1000. With these units, the devil is in the details of the multiple assemblies required to produce a 10-speed.

Bushing and sleeve failures plague these units with loss of pressure and other shift-related concerns. Wear on the sealing ring and hub bushing are some of the biggest causes of loss of charge pressure, which will lead to lockup and overheat concerns (Figure 1).

Figure 1 – Sealing Ring & Hub Bushing Wear

Concerned about a rattling noise coming from the bell housing? The early Ford and GM 10-speed converters work a little differently than your standard converter that use fluid pressure to push the lockup piston towards the engine. The early 10-speeds use fluid pressure to push the lockup piston away from the engine. The friction material is mounted to the turbine, and the reaction surface is in the impeller. (Figure 2).

Figure 2 – Impeller Reaction Surface & Turbine with Mounted Friction Material

Ford kept this design, but GM has transitioned to a more familiar captive clutch design. (Figure 3).

Figure 3 – GM Captive Clutch Torque Converter

This captive clutch design incorporates unique ways to dampen both cylinder deactivation and lockup feel, including an additional dampener. If you have ever heard a rattling noise coming from the bell housing in your GM truck, that’s the dampener rattling on the pivot pins at idle (Figure 4). The rattle starts when these pins and levers begin to experience wear, and the only solution is to replace the dampener assembly.

Figure 4 – Additional Dampener

Internal sealing ring and bushing wear is a common issue inside these transmissions as well (Figure 5).

Figure 5 – Internal Sealing Ring & Bushing Wear

Sonnax offers CDF drum saver kit 129910-01K to address issues in these areas like slipping, slide bumps, neutral conditions and ratio error codes.

Using the input and mating part, you can air check each drum to ensure proper sealing. This simple test will tell you whether you have any leaks in the apply of the clutch pack. It will also let you know if you have a leaking shaft. There are plugs in the shaft to block fluid and keep it in its intended circuit. If these plugs leak, it will cause shift concerns as well. Air checking the complete assembly before dropping it in the case will save you a lot of headaches. You can air check the assembly through the pump, which will allow you to catch any leaks before loading it in the case (Figure 6). The photo shown here has the assembly set on top of a Chrysler transmission case for convenience.

Figure 6 – 10L80 (Gen. 2) Assembly

Controlling the internal pressure loss will keep the wheels rolling down the road. Remember to use the proper fluid specifically designed to reduce friction and workload in the pump, either Dexron^® ULV or Mercon^® ULV. This is crucial because, like engine oil, transmission fluid is getting thinner as well. Using universal or previously designed fluid will result in shift complaints and premature failure. Attention to detail can save you headaches and comebacks.

As we see more 10-speed transmissions coming across shop benches, we’ll become more familiar with commonplace issues and how to diagnose and address them. Hopefully this article helps shed light on a few problems you might see — or want to avoid seeing — on your bench.

Caleb Perham is a Sonnax product support representative. He is a member of the Sonnax TASC Force (Technical Automotive Specialties Committee), a group of recognized industry technical specialists, transmission rebuilders and Sonnax Transmission Company technicians.