If it's never been off...and its not coming off with moderate, controlled use of a typical ratchet...you may as well stop.
If you use a breaker bar...you might twist the bracket and everything until the sun goes down...and it still wont be off. An impact is OK to use on this IF you are cautious and don't go at it like your removing frozen semi lug nuts.
Use a good quality 1/2" gun, as it takes a good jolt to free up the grip the oring has on the can. Find a tight fitting socket whether metric or standard. For mine I chose a 7/8" I believe instead of the 22mm normally used. It fit better based on my tools. Don't use any extensions...the lose a little power and absorb some of the impact. Put the socket directly on the gun. Hold one hand on the filter housing while hitting it to help absorb vibration and push it on there hard while hitting the trigger. Do it in short bursts (1 second) and watch for it to turn. Eventually it will come loose. Then finish removal with hand tools once it breaks loose. Don't impact the aluminum threads all the way off for removal. If it spins real fast it could gall the bare threads.
Perhaps a little propane torch heat would help expand the aluminum cup. But definately watch where the heat is going to avoid burning something else like a wiring harness. After you get it off carefully lube the oring with ATF or o-ring lube (if you have any). Just be careful not to "slop" anything in the can where the filter goes. You don't want cross contamination if not using ATF fluid on the oring. I applied a film coat of anti-seize to the cup threads. Then brushed/rubbed it in the metal with an old tooth brush. The oring seals up the cannister so the anti-seize cannot "leak" down in to the filter area even if you're a little sloppy on this step. This will ensure the next time it will spin right off with hand tools.
Reinstall by hand and just snug with a hand wrench. I think even hand tight would be fine. That oring grabs the can pretty good. I don't think an impact will harm the cannister as its pretty stout cast aluminum. It might polish up the points on the hex a little...but once its off you can make it easier to get off next time with a little effort and care.
Last edited by neil; 02-29-2012 at 07:42 AM.