When the loco arrived from Tyseley it was discovered that all the non-ferrous fittings were missing along with many other items, such as the motion, valve rods and piston rings. All these items had to be located, machined and fitted, along with many other parts including the ashpan, big ends, cladding and boiler tubing. Car manufacturer Rover helped out by bending sheet metal and creating the big end patterns.
However, very little work was required on the running gear because of the quality of 5637ís last overhaul shortly before withdrawal. It was the last Class 56xx to undergo a major overhaul in Swindon Works. The chassis was then reunited with the wheels and the water tanks and coal bunker refitted.
All the work necessary on the rolling chassis was undertaken, including refurbishing the motion, brake gear, steam and vacuum brake systems. Some of the restoration work was carried out by engineering trainees from the Swindon Skills Centre, who worked on restoring the coalbunker and side tanks. A new ashpan was supplied free of charge by a Midlands’ engineering company.
Several parts from other GWR locomotives were discovered on 5637, which illustrated how GWR workshops swapped standard parts around. They included the boiler from No. 5633, the regulator from No. 3024, the regulator stuffing box from No. 1160, the crossheads from No. 2251 and axleboxes from No. 6697
The final phase of the restoration, involved the repair and retubing of the boiler. Fortunately, the boiler proved to be in relatively good shape and major works were not required at the time. The bottom row of 57 steel stays were replaced, some welding carried out on the boiler shell, mudhole doors, washout plugholes and various parts of the front tubeplate.