The GM 8L90 8-speed automatic earned a reputation for torque-converter shudder under light throttle - a chuggy, gear-bag-of-walnuts feel between 30 and 60 mph. GM issued TSB 18-NA-355 prescribing a fluid swap to Mobil 1 Synthetic LV ATF HP, and most cases are fixed by that single procedure.
Common but cheap to fix. Most shudder cases resolve with the TSB fluid swap ($300-$500). Persistent shudder may indicate torque-converter wear, escalating costs to $1,500+.
Felt as a chuggy vibration between 30-60 mph under light throttle. Fixed under TSB 18-NA-355 by dropping the pan, replacing the filter, and refilling with Mobil 1 Synthetic LV ATF HP.
View P0700 Diagnosis →Hard, slamming shifts at low speeds. Often clears up with a fluid + TCM relearn. Stubborn cases may need valve-body service.
View P0700 Diagnosis →A small percentage of trucks still shudder after the TSB. Indicates torque-converter clutch wear. Repair is a torque-converter replacement.
View P2700 Diagnosis →Plastic transmission cooler line connectors at the radiator can crack and leak. Watch for red ATF on the driveway.
Run free diagnosis →1-2 second delay when shifting from Park to Drive after sitting overnight. Annoying but harmless on most builds.
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2015-2017 8L90 builds had the highest shudder complaint rates. 2018+ are much improved with the redesigned torque converter and fluid.
2018-2019 8L90 builds, or 2020+ vehicles that switched to the 10L80 10-speed (different transmission, generally better behavior).
Plan on the TSB fluid service at 50K-70K miles ($300-$500). Beyond that, regular fluid changes every 60K mostly keep the 8L90 happy. A worst-case torque-converter replacement is $1,500-$3,500.
If your 8L90 is throwing a check engine light, these are the codes most often associated with the problems above. Click any code for full diagnosis steps and typical repair costs.
It is GM service bulletin 18-NA-355, which prescribes draining the 8L90 fluid, replacing the filter, and refilling with Mobil 1 Synthetic LV ATF HP to fix torque-converter shudder. Cost at a dealer is typically $300-$500.
Like driving over a chuggy washboard between 30 and 60 mph under light throttle. Some owners describe it as a "loose gear bag" feel. It is most noticeable in lockup converter mode.
About 90% of cases, based on field reports. Persistent shudder after the fluid swap suggests the torque-converter clutch is already worn and needs replacement.
Every 45,000-60,000 miles is the conservative answer, especially with towing. GM's long-life schedule is much longer but most experienced techs recommend more frequent changes.
2015-2019 Silverado 1500, Sierra 1500, Tahoe, Yukon, Suburban, Escalade, Corvette C7, Camaro V8, and CTS-V.