Grind two flats on the slinger flange and use a big Crescent wrench on it. Remember it's got a left hand thread. The slinger will work just as well even if it's not completely round- - - -maybe better. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Here is the tool you seek. Ad description says it fits Muncie 4 speeds M20/M21/M22, which all use the same retainer nut as in your 3 speed (GM# 591150).
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
I have cut a similar wrench from an old steel framing square. Good metal.
~Charley 1954 Chevy 3100 with 235 261 project engine “Ole Blackie” Follow along in the DITY 1963 Chevy half ton stepside short box 230 1954 GMC 3 ton 302 And several more Chevy camper and work trucks 1979 1987 1996 1931 Packard car, 327 i 8 auto
Not quite sure if my images are legible or not, even if they come out, but here is an old stainless steel wrench I fabricated while still working for Lockheed, right now I have it loaned to another friend of mine. I believe it is .125" thick.