GM Service Manual Online
For 1990-2009 cars only

Harsh Shift D4 to D3, D2, or D1 for Chevrolet Chevy C Silverado - 2WD 2006

Checks

Cause

Spring Assembly (506)

Not functioning

Checkball Orifice

Plugged

Snap Ring (511)

Not seated

Scan Tool Shift Adapts

Maximum shift adapts