Got transmission out yesterday, rear main seal housing removed, new seal and slinger installed. And Transmission back in....now to spend fathers day getting all rest back in. On the original main topic of the SLINGER? like so many finds I dont see its purpose other than maybe a way to keep any debri from gaining access to the rear main. The slinger firmly mounts to the body of the crankshaft but they freely spins within the rear main seal housing. The rear main itself is a very loose fitting 1 seal surface seal. The type of seal that a small amount of anything could cause pre-mature failure. Do they make a diff type of rear main seal that is a dual seal stiffer type, dunno couldnt find one went with OEM. Only way I would leave the slinger off is IF I were to be able to find a more rugged looking rear main seal. My pic attached of the rear main you can see the single lip configuration.