Billet replacement for the GM 8L90 cooler thermal bypass valve, OE 12507100, so fluid reaches the cooler instead of sitting behind a stuck thermostat.
Watching the transmission temperature on a 2015-2018 Silverado 1500, Sierra 1500, Tahoe, Suburban, Yukon or Escalade climb every time you tow or sit in summer traffic? On the 8L90 the first part to look at after the cooler lines is the thermal bypass valve, the thermostat that decides whether fluid goes through the cooler or skips it. This is a billet aluminum replacement valve cross-referenced to 12507100, with a magnetic service plug sealed by an O-ring, for 8L90-equipped trucks and SUVs in those years.
Cold fluid does not need cooling, so the factory valve routes it past the cooler until the transmission warms up. GM bulletin 22-NA-182 lists the 8L90 valve as mounted outside the transmission and opening at 194 F (90 C), which is higher than the 158 F (70 C) valve on the 6L80 and 6L90. Once the element is open, fluid is supposed to run through the cooler and come back to the case cooler than it left. If the thermostatic element weakens or sticks, the cooler sees little or no flow at exactly the moment the truck needs it, under load and in heat. The billet body here takes the place of the factory valve, and the magnetic plug gives you a place to catch wear metal in the cooler circuit and a way to inspect it at service time.
GM's own order in bulletin 22-NA-182 is cooler line first, valve second. A twisted rubber cooler line on a low-mileage truck causes the same harsh shift, shudder and overheat complaints, so inspect the lines, untwist or replace them, and set the fluid level before you condemn the valve. Our 8L90 cooler line replacement guide walks through that exact split. If the lines are straight and the truck still runs hot, compare temperatures on each side of the cooler once the fluid is past 194 F; a valve that never opens shows up there. Shudder that stays after the cooling side is fixed usually points to fluid or the converter clutch, covered in 8L90 common problems and fixes.
The listing covers 2015-2018 Chevrolet Silverado 1500, Tahoe and Suburban, GMC Sierra 1500 and Yukon, and Cadillac Escalade with the 8L90. Many of these trucks were also built with a 6L80 in the same years, and the 6-speed uses a different valve, so confirm the transmission RPO on the glovebox or door label. The 12507100 number is the cross-reference the maker uses for the 2015-2018 8L90 valve; it is not a GM dealer part number we could verify, and later trucks use a different valve, so the safest match is to compare against the valve on your truck or send us your year and VIN. Everything else for these units is on the 8L90 / 8L45 parts page.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
GM bulletin 22-NA-182 lists the 8L90 valve as external to the transmission and opening at 194 F (90 C). The 6L80 and 6L90 valve opens at 158 F (70 C).
This valve is listed for 2015-2018 trucks. Later 8L90 trucks use a different valve, so send us your year and VIN if you have a 2019 or newer model.
Yes. GM's bulletin names a twisted cooler line as a common cause of overheating and shudder on low-mileage trucks, and tells technicians to check the lines first and the valve second.
It catches steel wear particles flowing through the cooler circuit. Pull it at fluid service time to check for debris and clean it before reinstalling.
There is no dipstick on the 8L90. With the engine running and the fluid at 35-45 C (95-113 F), remove the check plug and add DEXRON HP until it just drips out.
