The repairs have been completed and traffic is beginning to return to normal, but drivers still face residual delays of around 45 minutes, say Highways.
Two lanes (1 and 2) were closed between junctions 26 (Orrell Interchange, M58) and 27 (Standish, Parbold) for around an hour before reopening at 12.15pm.
The disruption led to three miles of queuing traffic and 50 minute delays for those travelling towards Lancashire.
National Highways said the closure was due to "a carriageway defect" which required urgent repair.
In its latest update, the agency said: "Emergency repairs are complete and all lanes are now open on the M6 northbound J26 (M58) to J27 near Wigan.
"There are residual delays of at least 45 minutes above usual journey times, however, these are easing and normal traffic conditions are expected to resume shortly."
