Replaces the shudder-causing regulator valve and springs in a GM 8L90 valve body, curing torque converter shudder and the 1-2 clunk on 8L45 and 8L90 units.
If your 2015-up Silverado, Sierra, Tahoe, Yukon, Suburban, Escalade, Camaro or Corvette with the GM 8L45 or 8L90 eight-speed has a low-speed vibration between 25 and 45 mph that feels like driving over rumble strips, or a hard clunk on the 1-2 shift and on reverse engagement after the truck sits, the cause is not always the torque converter. This is the Superior STL-8L90 valve body correction kit, which installs into your existing valve body and swaps in heavier engineered parts at the specific location that causes both problems.
The GM 8L45 and 8L90 valve body runs a regulator valve and spring arrangement that controls torque converter clutch apply pressure. As the bore wears, that regulator loses control of TCC pressure, which is what owners feel as a low-speed shudder rather than a smooth, locked converter. The same wear pattern can crack the valve body casting and produce a hard clunk in the 1-2 upshift and in reverse engagement, especially on the first shift after the truck has been parked. The STL-8L90 kit replaces the worn regulator valve and springs with heavier engineered parts at that bore and includes the drill bit needed to open one hydraulic passage during the install.
Diagnose before you buy. If the torque converter itself has genuinely failed, no valve body correction kit fixes a shudder caused by converter clutch material. Our 8L90 valve body symptoms guide covers how to separate a valve body-caused shudder from a converter problem, and our 8L90 common problems and fixes guide covers the fluid condition check GM recommends before replacing any hard parts, since contaminated fluid alone causes similar shudder complaints.
This kit fits the GM 8L45 and 8L90 eight-speed, 2015 and up, which covers Silverado and Sierra 1500, Tahoe, Yukon, Suburban, Escalade, Camaro, CT6 and Corvette depending on year and engine. Manufacturer part number is STL-8L90. Full fitment and every other 8L90 and 8L45 part we carry, including a complete remanufactured valve body if yours needs more than a correction, is on the 8L90 parts page.
The valve body can come out with the transmission still in the vehicle after draining the fluid and dropping the pan and filter. The two aluminum bolts holding the oil pump chain cover are torque-to-yield and must be replaced during reassembly, not reused; GM lists them under part number 11548404. You will need an E12 socket for the valve body bolts, and the tapered top on that socket usually has to be ground down to get full engagement without rounding the bolt heads. Expect stored codes after unplugging the internal wiring harness to pull the valve body; clear them on the first start after reassembly. While the valve body is out, this is also a good time to install a solenoid kit if the originals are high-mileage, and a sealing ring expander and resizer kit makes reseating the valve body sealing rings easier on reassembly. If the correction kit does not fully resolve the complaint, a full remanufactured 8L90 valve body is the next step.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It is a correction kit that installs into your existing valve body. You remove the valve body, swap in the heavier engineered regulator valve and springs at the problem location, drill one passage with the included bit, and reassemble.
If the shudder is caused by the valve body's regulator valve losing control of TCC apply pressure, yes. If the torque converter itself has failed, this kit will not fix it. Diagnose before you order.
Yes. It is built for both the 8L45 and 8L90, 2015 and up, which share the same valve body family and regulator valve layout.
No. The valve body can be removed with the transmission in the vehicle after draining the fluid and dropping the pan and filter.
An E12 socket for the valve body bolts, usually with the tapered top ground down for full engagement, plus the two torque-to-yield oil pump chain cover bolts (GM part number 11548404), which must be replaced and not reused.
The same regulator bore wear that causes TCC shudder can also crack the valve body casting, which shows up as a hard clunk on the first 1-2 shift or reverse engagement of the day. This kit corrects the wear point that causes it.
