GM 10L1000 Casting Identification & Clutch Application

In 2019, GM introduced the 10L1000 transmission. It was the latest evolution of the 10L series that continued into 2020 with the second generation of 10L60, 10L80, 10L90 units. The 10L series has seen substantial changes. With the 10L1000 and Gen. 2 units, there was a different clutch application, no latch valves (Figures 1 & 2) and a few other new features. Note that Ford did not make clutch application changes to their similar 10-speeds. This article focuses on the 10L1000.

Figure 1 – 10L1000 Upper Valve Body Valve Lineups

Figure 2 – 10L1000 Upper Valve Body

GM 10-Speed Clutch Application Changes

GM also made some changes to the lower casting, adding checkballs (Figure 3). These checkballs take the place of the latch valves and help control clutch regulation. The checkballs are in line with the feed limit valves. Feed limit low is 95–119 psi, and feed limit high is 145–181 psi. The feed limit low controls the “A” and “B” clutch circuits while the feed limit high controls the “C” and “F” clutch circuits. When the pressure exceeds the limit pressure, the checkball unseats and allows the control valve to stroke. This will bring clutch apply pressure up to line pressure much faster.

Figure 3 – 10L1000 Lower Valve Body Checkball & Small Parts Locations

The feed limit low valve also controls solenoid feed for the default solenoid. When the wear occurs in the balance end of the feed limit low valve, this causes solenoid feed pressure to drop at the solenoid, putting the vehicle into a partial default mode. This can allow more than four clutches to apply, causing a bind-up condition. The default solenoid is an on-off solenoid and is normally on. When it’s off, the vehicle is in default mode. This solenoid controls the default enable valve and default select valve. These two valves also control line pressure feed to the “F” clutch circuit.

To learn more about 10L series clutch regulation, read “Understanding ’19-Later GM 10-Speed Clutch Regulating Changes.” The feed limit valves, transmission problems associated with GM Safety Recall N242480630 and how to address wear with Sonnax feed limit low valve kit 105740-54K are explained in “Understanding the ’19-Later GM 10-Speed Safety Recall.” Both articles are written by Sonnax Product Line Manager Jim Dial.

In 2023, GM changed the 10L1000 valve body casting walls to be thicker in the pressure regulator section. Under elevated line pressure, the thin walls of the worm tracks in early-style castings would crack and break (Figures 4 & 5).

Figure 4 – Early-Style 10L1000 Casting PR Section (Thin Walls Easily Broken)

Figure 5 – Late-Style 10L1000 Casting PR Section (Thick Walls)

Caleb Perham is a Sonnax automotive technical specialist. 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.