The two 1970s carriages left the Central Tramway in January for refurbishment at Rotherham specialists Wheelsets UK, and their departure was the first time the tracks have been empty since the funicular railway opened in 1881.
Previously maintenance was carried out on-site by the Tramway's own engineers.
They were due to return in March, but setbacks with the rejuvenation work meant they were instead delivered on May 4.
Foreshore Road was closed from 6am between the Spa Bridge roundabout and Eastborough to allow a 50-tonne crane to lift the carriages back onto the rails ahead of the summer tourist season.
Project leader Martin Hudson from Wheelsets UK said: "There's been a 4/5 week delay from the initial schedule due to issues with the fabrication and galvanising of the new chassis but we're confident that the upgrade will be well worth the wait.
"This has been a very challenging project with many hidden surprises along the way, along with the inevitable daily delays and difficulties due to current issues with the supply of equipment and services.
"At Wheelsets UK we’ve done our best to meet the company's targets despite some setbacks, working weekends and long hours at the workshop. We are confident the owners and public will be impressed and even safer by the end result.”
The lift to and from South Bay has been shut since the start of the year while the biggest overhaul in 50 years took place. Some of the tramway's infrastructure dates back to the early 20th century, when the system was first converted from steam to electric power.
The 1930s chassis has been fully replaced, new emergency brakes that can be computer-controlled fitted, and the carriages given major attention for the first time since the Olympia fire damaged the tramway over 40 years ago.
Current chairman Neil Purshouse's family took a stake in the business in the 1960s, but it has been operating since 1881 and is still owned by the company that first registered it. It was electrified in 1920 but has undergone surprisingly few technological upgrades since before World War Two.
The carriages will benefit from new floors, ceilings, lights, seats and brakes, as the vehicles suffer badly from weather-related corrosion in their exposed cliffside location - as well as damage caused by seagull droppings.
Despite their age and layout dating back to the steam age, the station and carriages are surprisingly disability-compliant, with the spacious interiors and lack of steps meaning managers have only had to fund improvements such as hearing loops for the modern customer.
Scarborough Central Tramway history
The machinery has had 10 new shafts fitted, but otherwise is relatively unchanged since it was first installed in the Victorian era.
The cars are no longer manually operated - in 2009 an automated traction system and more powerful motor were introduced to improve safety and smooth acceleration.
Yet the lift has an almost-impeccable safety record over its operational history - the only fatality occurred in 1927. There are 12 staff.
The tramway's popularity has remained 'very stable' over the decades, with between 450,000 - 500,000 passengers using it every year.
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