GM 24053920 valve body service kit with bonded spacer plates, gaskets and check balls for 6T-series six-speed automatics in Encore, LaCrosse and Envision.
If you have the valve body off a Buick Encore, LaCrosse or Envision six-speed for a cleaning, a sticking valve or a solenoid body swap, this is the GM kit that puts it back together sealed. GM service kit 24053920 supplies the bonded spacer (separator) plates, the channel plate gasket, the side cover gasket, the filter seal, and the check balls and small valve body hardware that come loose when the body is split. It supersedes the earlier kit 24042856. It is a reseal kit, not a valve body casting, so your original control valve body and solenoid body go back in.
The 6T40 family stacks three layers: the case, the separator plate, and the control valve body, with the solenoid body and TEHCM bolted on top. The separator plate is what keeps dozens of oil passages apart. Its holes and orifices meter oil from one layer to the next, and the check balls seated against it decide which way oil can flow in circuits like the clutch feeds. The gaskets are bonded to the plate, so once they have been torqued, heat-cycled and peeled apart they do not seal reliably a second time. A plate with a torn or compressed bead lets pressure cross-leak between circuits, and on a clutch-to-clutch transmission that shows up as flare, slip and pressure codes even though every solenoid tests good.
Those same symptoms also come from a cracked 3-5-R wave plate, a worn pump or pressure switch failures in the TEHCM, so a new gasket set is only part of the answer when the hard parts are damaged.
If you are already pulling the valve body, buy the kit, because the old plates should not be reused. If you are still deciding whether to open the transmission, read our 6T40 valve body symptoms and testing guide first. With the valve body out, air-check the clutch passages in the case using low regulated air; Sonnax publishes the port locations for each generation. A circuit that holds air on the case side but still flares on the road points back to the valve body side and the plate between them. Our 6T40 common problems guide covers the wave plate and pump failures that need to be ruled out.
GM lists 24053920 for the Buick Encore 2013-2022, LaCrosse 2012-2019, Envision 2016-2020, Cascada 2016-2019 and Envista 2024-2026, along with other GM models on the same six-speed family. That spread covers more than one generation of control valve body, and Sonnax warns that Gen 1 and Gen 2 or Gen 3 valve bodies do not interchange. That is why GM fits this kit by transmission RPO. Check the RPO on your glovebox or door sticker, or send us your year and VIN and we will confirm it before it ships.
If you are replacing solenoids at the same time, the 7-piece 6T40 solenoid kit covers early units, and a new 6T40 TCM must be programmed for your vehicle before it will shift correctly.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. GM 24053920 is the reseal kit: bonded spacer plates, gaskets, a filter seal, check balls and small hardware. Your original control valve body and solenoid body are reused.
Yes. GM lists 24053920 as the replacement for the earlier kit 24042856.
GM fits this kit by transmission RPO, not by model name alone, and the listing names Buick applications. The same six-speed family is used across many GM cars, so send us your VIN and we will confirm the RPO matches before it ships.
Use DEXRON VI. GM lists a fluid change capacity of about 4.2-6.3 quarts for the 6T40, but the final level is set at the check plug with the engine idling and the fluid at 185-203 F. Overfilling can push fluid out of the vent.
Yes. Reset the transmission adaptives with a capable scan tool and run the service fast learn. Expect some soft or firm shifts for the first 10 to 15 shift cycles while it relearns.
