Expert Cadillac CT4 transmission service in Chicago. Free computer diagnostic, 2-year / 24,000-mile warranty on rebuilds, all years.
We will contact you as soon as a service member is available by call, text, or email.
2020 - present: 8-speed automatic (8L45 or 8L90) depending on engine; RWD and AWD CT4 2.0T: 8L45 8-speed; 237 hp CT4 2.7T: 8L90 8-speed; 325 hp CT4-V 3.6T: 8L90 8-speed; 360 hp; performance-tuned shift calibration CT4-V Blackwing: 6-speed manual only (no automatic offered)
CT4 diagnosis uses GDS2 for full manufacturer codes. Dexron HP fluid requirement is non-negotiable - Dexron VI causes shudder in both 8L45 and 8L90. Software version check is the first step for shift harshness complaints. 8L45 shudder diagnosis includes lock-up clutch test at highway cruise. Torque converter replacement resolves persistent shudder. AWD transfer case noise is isolated by coast-down test and axle disconnect check. Pan seal leaks after service are common if a reusable pan gasket was not replaced - we use new gaskets on every service.
GM Dexron HP ATF (required - not Dexron VI), approximately 8 - 9 quarts per unit
Verify exact spec on the dipstick label or owner's manual before fill. Recommended change interval: every 60,000 miles for normal driving, 30,000 miles under severe service (towing, stop-and-go, hot climates). Pan service typically takes 6 - 8 quarts; a full fluid exchange takes 10 - 14 quarts depending on cooler-line capacity.
Fluid service: same day; software update: same day; torque converter: 2 - 3 days; AWD transfer case service: same day; full rebuild: 4 - 6 days
Every vehicle needs diagnosis before anyone can promise a repair path. These are the situations we help organize before you decide what to do next.
Tell us when it happens, whether reverse still works, and if warning lights are on. A scan and fluid check come before guessing at a rebuild.
Fluid condition, leak location, and driving distance matter. If the vehicle is slipping badly or overheating, towing may be the safer next step.
A failed solenoid, valve body, converter, or internal clutch problem can lead to very different repair paths. The goal is a clear diagnosis and written estimate.
The CT4 uses updated 8L45 and 8L90 units compared to the 6L45/6L50 in the ATS. The 8-speed offers smoother, more frequent gear changes. Both share the Dexron HP fluid requirement.
Cold ATF is thicker and valve body solenoids respond slower until fluid warms up. Brief hesitation in the first 1 - 2 minutes on sub-zero mornings is normal. If hesitation lasts longer or is accompanied by codes, valve body inspection is warranted.
The CT4-V uses the 8L90, which has higher torque capacity and more aggressive shift calibration than the 8L45 in base models. The CT4-V Blackwing is manual-only and has no automatic transmission.
TCM reprogramming for performance is available, but we recommend stock calibration for daily-driven vehicles to preserve drivability and warranty coverage. Performance tuning is discussed on a case-by-case basis.
Every 40,000 - 45,000 miles with Dexron HP for city driving. GM's 'lifetime' fluid claim is based on ideal highway conditions - Chicago stop-and-go generates more heat cycles and requires more frequent service.
Same-day appointments available. Honest estimates, no surprises. We've been doing this since 1987.
