At the 2013 Orange Spectacular Dave Buttjer and Jim Palmer Jr. gave a Snap-Coupler safety seminar. They covered the basics on how to use the hitch system on the WD/WD45 tractor, as well as some safety tips. The Snap-Coupler hitch was equipped on ten Allis-Chalmers tractors from the factory:
B, CA, WD-45, D-10, D-12, D-14, D-15, D-17, D-19, 190 ( WDs could be converted to Snap-Coupler but did not come standard).
Snap-Coupler Parts Diagrams
Check out the AGCO Parts Book for a complete breakdown of parts. Hooks springs and lift-latch repair kits are available through DJS Tractor Parts, Steiner Tractor Parts or your local AGCO Dealer.
Equipment Inspection
Check Snap-Coupler bell for dents, cracks or damage. If there are any signs of these defects consider replacing your Snap-Coupler bell.
The Snap-Coupler hook can wear thin after years of use, so check it to see if it can still pull implements without slipping out. The pivot pin holding the hook can also wear after extensive use. Replace the pivot pin if it appears to be badly worn. The hook spring needs to hold the hook up into the bell and snap into place when the implement is attached. A worn or broken spring will not hold the hook in place and the implement tongue will come out.
The disconnect lever and linkage needs to be free moving. Check the lever to ensure that it is not holding the hook open. Tractors equipped with the chain-type linkage need to have slack in the linkage to prevent the hook from releasing the implement tongue from the tractor.
Lift-arm latches must be free moving and be easily opened by hand. Proper spring tension is required, and some latches may require lubrication. The lift-arm latches are firmly secured to the lift arms on the tractor by tightening the set screw and jam nut.
Safety and Operation
Always take the time to be certain the implement is hooked up correctly. Hastily hooking up Snap-Coupler implements could lead to an oversight in the process that may lead to an accident.
When using ground engaging implements, hook a chain around the drawbar of the implement and then attached it to a solid area on the tractor. The chain will prevent the implement tongue from dropping into the ground if it detaches unexpectedly.
If possible, hitch Snap-Coupler implements on firm, level ground. Be sure the tractor brakes are applied before dismounting the machine to hook-up lift arms.
When re-attaching the tractor drawbar be sure the tighten it down to the drawbar guide. This will prevent movement when pulling trailed equipment.
Questions?
Comment below for questions about using the Snap-Coupler hitching system or about getting parts.
Austin M. Frederick 
The snap coupler bell tends to wear over the years. To check for excessive wear, push up on the rear of the bell and watch the latch hook. If the hook follows the bell all the way through upward travel, you are good to go. If the hook stops raising BEFORE the bell stops, you will need to replace the bell, or weld the top rails back up where it is worn.
Tractor “breaks” are a bad thing. Tractor “brakes” help you stop 🙂
Ooops! Thank you for the heads up, Charlie. Sometimes little oopsies get past me.