No Second And Sixth Gear

WARNING: This page is about a different car, the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, 2018 Chevrolet Suburban 3500 HD, and 2018 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.

Checks	Causes
A/Trans Fluid Pan Assembly (29)	Verify proper fluid level and condition, inspect transmission assembly for leaks.
Control Valve Upper Body Assembly (304)	Inspect for sticking, damaged, or worn 2-6 clutch regulator valve (334) and spring (326).
Control Solenoid (w/Body and TCM) Valve Assembly (314)	Pressure control solenoid 4 commanded/failed LOW (off) or leaking - Perform solenoid valve assembly function test. Refer to Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test .
Center (with 2-6 Low and Reverse Clutch) Support Assembly (67)	Inspect for proper installation of the 2-6 clutch return spring retaining ring (455). Inspect for damaged 2-6 clutch piston assembly (457), spring (456), retaining ring (455), and center support housing (459). Inspect for worn or damaged 2-6 clutch plates (451 - 453).
Center Support Fluid Passage Seal Assembly (20)	Inspect for worn, cut, or damaged seals. Inspect for proper seal (20) size (6L45/50E MYA/MYB) vs (6L80/90E MYC/MYD).