Understanding the ’19-Later GM 10-Speed Safety Recall

In March 2025, GM issued Safety Recall N242480630 for the GM 10L1000 and Gen. 2 10L60, 10L80 and 10L90 transmissions. This recall involves several different applications of cars, SUVs and trucks. The recall states that vehicles with the listed 10-speed transmissions may experience a “Momentary Wheel Lock-up” condition at higher speeds that could also include a downshift back to 2^nd Gear. This recall states that a control valve in the valve body can be susceptible to excess wear over time, resulting in a gradual loss of control pressure. This loss of pressure is coming from the feed limit low valve (Figure 1).

Figure 1 – 10L1000 Feed Limit Valve Locations

This valve is part of the boost ball circuitry, which we recently featured in an article, but this valve also has another job: to be a limit valve for solenoid feed to the default disable (DD) on-off solenoid (Figure 2).

Figure 2 – Default Disable Solenoid

The DD solenoid controls two valves in the upper valve body: the default enable valve and the default select valve (Figure 3). These two valves are primarily used for a power-down default drive mode, which would equal 2^nd Gear in a Drive range and Reverse. The DD solenoid is powered on at all times and does not turn off until a default event occurs.

Figure 3 – 10L1000 Default Select & Default Enable Valve Locations

These 10-speed transmissions have an interesting design feature that allows pump output pressure to be directed through the two default valves into the exhaust passages, which, in turn, applies the clutches when the DD solenoid is off. Figures 4 and 5 show normal function of the DD solenoid and abnormal function with the exhaust passage pressurized.

Figure 4 – Default Disable Solenoid Normal Function

The feed limit low and high valves are in line with the boost check balls that help control clutch regulation. The feed limit low valve also connects to the DD solenoid, which acts as a solenoid regulator valve limiting the amount of solenoid feed. The DD solenoid controls the valve positions of the default enable and default select valves, which both direct exhaust backfill pressure to a relief valve when the DD solenoid is on. When the DD solenoid is off, these two valves direct line pressure to the exhaust backfill circuit apply clutches through the exhaust ports, which is a default strategy.

Figure 5 – Default Disable Solenoid Abnormal Function

The feed limit low has a history of high wear at low vehicle mileage. This creates low solenoid feed to the DD solenoid controlling the valve positions of the default enable and default select valves. When solenoid feed pressure is low, the two valves can allow the transmission to drop to lower gears or even create a bindup condition, depending on solenoid application/gear command. When the DD solenoid is off in a no-power condition, the ABCD clutches are applied through the default disable valves, through their exhaust ports, which is 2nd Gear.

The main issue is that when the low limit valve wears, it can create low pressure to the DD solenoid which controls the two default valves. This can cause several complaints, especially when hot. The most common complaints occur, when shifting into higher gears like 7^th or 8^th: the vehicle suddenly drops to 2^nd Gear or the drive wheels suddenly try to lock up. One thing that has been noticed is that vehicles with a 10L1000 can have low limit valve wear out in as few as 35K miles, especially vehicles that are tow trucks or haul large trailers. A quick check for something like this is to let the vehicle cool off. Most of the time, the transmission will function normally until hot. Caution: Extended driving in these conditions will destroy clutch packs in the transmission, as this wear will cause the unit to bindup at times. Another indication that this is the problem is that there will be a trouble code P0747, which basically says that the “E” clutch is on when it should be off. Sonnax offers drop-in feed limit low valve kit 105740-54K to restore valve function and prevent future wear in the 10L1000 as well as Gen. 2 10L60/80/90 units.

Sonnax Feed Limitr Low Valve Kit – 105740-54K

The safety recall has a software update that will put the transmission into 5^th Gear when the TCM sees bore wear starting to occur and turn on the check engine light. It will give the driver the ability to get off the road. The next key cycle will allow the driver to start in 1st Gear as long as the transmission is capable. This software update will help prevent road hazards, but the real issue is still wear in the low limit valve that is not capable of holding the two default valves in check.

A simple way to test for wear is to vacuum test the balance end of the valve (Figure 6). This is the location that typically wears the most. The vacuum test should match the feed limit high. These are both the same valve trains but have different springs. A typical reading on a valve like this is 18"-Hg or higher.

Figure 6 – Feed Limit Low Valve Vacuum Testing

Jim Dial is a Sonnax product line manager. 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.