STL010 Transmission Cooler Bypass Kit with Integrated Gasket – Cooling System Upgrade for GM 6L80 / 6L90 / 8L90 Transmissions

Everything you need comes in one box: the precision-engineered Superior STL010 thermo-bypass valve and a high-quality gasket. Simple installation, durable materials, and reliable performance—built to take whatever you throw at it.

• 【No More Dry Starts】 A smart bypass valve automatically primes the transmission cooler the moment the engine turns over. Whether you just swapped the fluid or finished a rebuild, this keeps everything lubricated from the very first second—no waiting, no worry.
• 【Stays Cool Under Heavy Load】 Running hot is the fastest way to kill a transmission. This upgrade cuts average operating temperatures by up to 20%, giving you a serious cooling advantage when you’re towing, hauling, or crawling off-road. Less heat means less stress on every component.
• 【Check Fluid Instantly】 Forget idling the engine just to get a fluid reading. This setup lets you verify transmission fluid level immediately after installation. No warm-up, no guessing—just a clean, accurate check that gets you on the road faster.
• 【Everything You Need, One Box】 No hunting for extra parts. This kit comes with the Superior STL010 thermo-bypass valve and a high-quality gasket—all engineered to fit right and hold up. Simple install, durable materials, and reliable performance you can count on.
• 【Less Fluid Breakdown, Fewer Repairs】 Keeping transmission temps lower and more consistent directly slows down fluid degradation. That translates to longer ATF life, healthier internal parts, and fewer trips to the shop. Built for guys who want to avoid expensive rebuilds down the line.