I bought this tool to work on a 4L60E gearbox. It works great by compressing the spring on the low/reverse piston to release the locking ring on the back of the case. Also great for compressing springs and removing snap rings on the reverse input drum. For a 3-4 intake body this won't work because there is no threaded rod hole in the barrel so I have another tool for that. I've added a few photos of this instrument on the inverted input drum, front and back.