To install Gauge 1 couplers on an Aristo-Craft GP-40, purchase a set of Kadee 1787 or 1788 or 1789 couplers. The couplers and gear boxes in these sets are the same.
The only modification required is to enlarge the hole in the rear of the gear boxes with a 15/64th inch drill bit so they will fit over the coupler mounting posts on the diesel. If you do not have a 15/64th inch drill bit, a 1/4 inch bit will do. Assemble the Kadee couplers as illustrated in their instructions.
To remove the Aristo-Craft couplers, place the diesel upside-down in a foam cradle or rolled towels, taking care not to damage the horns. Remove the small chrome screws and return springs behind the mounting posts. Remove the chrome screws and washers from the mounting posts and set them aside, as they will used to mount the Kadee couplers. Turn the diesel over and remove the small black screws on top of the couplers just behind the knuckles. Remove the knuckles, and then the plates that held them to their mounting posts. Re-assemble the knuckle couplers and place them, their return springs and their small chrome screws in a Ziploc bag. Mark the road name, GP-40 and the road number on the baggy and store them in the diesel’s packaging.
After the Aristo-Craft couplers are removed, turn the diesel upside-down in the work cradle. Slip the Kadee couplers through the slots in the pilots and over the mounting posts. Fasten the couplers with the original Aristo-Craft washers and screws.
CAUTION: Do not use the #4 screws provided by Kadee as they will split the mounting posts on the diesel. Use only the original Aristo-Craft washers and screws, when mounting Kadee couplers on the posts of ANY Aristo-Craft diesel.
The couplers will fit to the proper height and provide a wide swing without any modification to the pilots of the diesel.