Loftus Bank will be closed to traffic for nine weeks as the final stage of work gets under way to stabilise the road link for another 120 years.
Repair work is due to start at the end of next month, presenting a massive engineering challenge as a retaining wall is built at the top of the bank.
Engineers from Redcar and Cleveland Borough Council said they hoped the work would be completed by the end of September. Staff will work at the site seven days a week from 6am until 10pm.
Problems started last March after extensive flooding led to landslips.
Work to repair the bank started in December and it has remained open to light traffic for much of the time.
The route has had to be closed occasionally since then, because of serious movement of the waterlogged land.
The road has to be removed to a depth of seven metres. It will be replaced when the the retaining wall, which is 60 metres long and seven metres high, is constructed.
Before the road is closed, the council said it intended to introduce traffic calming measures in North Road and Hummersea Lane in Loftus and in Skinningrove.
More than 1,000 homes and businesses in the Loftus, Easington, Liverton Mines, Carlin How and Skinningrove areas have received leaflets from the council on the latest developments.
The council also intends to hold meetings with Loftus Town Council, the town's business association and the local road safety committee. In a letter to residents, Councillor Sylvia Szintai, lead councillor for environment and infrastructure, said: "The final part of the work is regrettably going to be the most disruptive.
"We think the road closure will start towards the end of July for completion at the end of September. It helps that for much of this period the schools will be on holiday and traffic at its lightest. Hopefully, the weather will also be kind."
Coun Szintai said: "Once the installation of the culvert at the bottom of the ravine was completed, the placing of imported fill to rebuild the valley walls has rapidly allowed operations to approach road level."
Inspector Mick Bennett, from Cleveland Police's traffic department, said the work was going to make the A171 Guisborough to Whitby moors road busier
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