The ramp, which links the Décarie Expressway to Highway 15 south leading to the Champlain Bridge, was to be closed to heavy trucks as of 11:30 p.m. Tuesday.
The restriction applies only to trucks weighing more than 4,500 kilograms.
Cars, buses and emergency vehicles can continue to use the ramp.
But the six-kilometre truck detour, via Highway 20 and the Angrignon Interchange, could exacerbate traffic problems in the area.
Engineers who monitor the Turcot advised on Monday that cracks in the structure had to be repaired immediately, a Transport Quebec spokesperson said.
The two-lane, 750-metre-long ramp is used by about 31,000 vehicles daily.
Repairs are to begin Wednesday, with work expected to be completed by the end of January.
The ramp in question is scheduled for major repairs next year.
In April 2010, structural problems on the same ramp forced Transport Quebec to close one of its two lanes for several weeks, causing major traffic headaches.
Turcot inspection reports made public last month showed engineers have given all 35 of the structures in the Turcot Interchange and adjacent structures the worst grade possible.
Quebec is spending $254 million repairing the structures until they can be torn down after replacements are built as part of the $3-billion Turcot reconstruction.
That project is to begin in 2012 and be completed in 2018.
In December 2010, Transport Quebec barred trucks from the Mercier Bridge over safety concerns. That ban was lifted in September.
.Have Fun and Remember Verdun..........................Cheers ! -Les