[tall terry]

The best tool to remove those screws, is a high quality 3/8" drive, T27 socket,, in an air powered 3/8" impact wrench, like an ingersol... it's what we use in the shops....
An impact driver is a good to have tool,, it sometimes can break a screw loose if you do not have access to an impact wrench..

he doesn't say he has damaged the torx head,, so all the methods to remove damaged fasteners are indeed helpful, as was the one I had posted,,, but we are getting ahead
of ourselves...

usually the problem is cheap poorly made torx tools, followed by scamming out while applying force... leading to the drill... the drill is always my last resort. after all else fails... I have seen home mechanics cause extensive damage with a drill, slipping of the steel bolt and punching a hole in the softer aluminum

 

[tall terry]

009 you are absolutely.correct on both assumptions....

The screws are loctited in, drilling the heads, will only create further problems... like taking the outer primary off, and using a drill press to drill a straight hole.. ez outs dont do well.with loctite..

.if you drill the heads, use a 1/4" drill bit, and drill.straight into the torx head,,, the head will break.off, as soon as you reach the threads. Don't bother with all that increasing bit sizes,, get the head off and take it from there..

 

[tall terry]

at this point,, get out the drill... use a 1/4" bit, drill straight into the torx head area,,,, when the bit clears where the head changes to threads, the head will snap off, and remain on the bit... stop drilling as aoo as the head breaks off...
after you have the derby cover off, you may attempt to remove the screw with a good pair of vice grips,, after hearing the screw to appx 400°F with a propane torch... or,,,,

If there isn't enough screw protruding,,, and depending on your skills with a drill,, (no offense, but by the trouble you've had with this, so far, I would say low),,, take the cover off and use a drill press to insure you drill a straight hole.. start at about 1/8" and go up incrementally until you reach the correct diameter hole for the screw extractor,,, remember to heat the screw, before attempting to remove it..

snapon makes a really great extractor set.. ... i highly recommend it, or you can buy just the size you need,,, snapon sells to the public through a web site, or over the phone...
The part # for the tool that extracts 1/4" screws is #E1 you will need a sharp drill bit in addition to this tool...

 

[tall terry]

if the torx heads are thoroughly trashed it's time to get the drill out
..i would suggest a 1/4" left hand bit.. one of 2 things will occur,, the bit will catch the screw head and spin it out or after going about 1/8" in the heads of the screws will come off....then remove the derby cover and proceed... the E1 snapon screw extractor would be my choice if it becomes necessary... it may be possible to use vice grips and heat to melt the loctite..

all the popular methods have been offered,, the rest is up to the OP... if the screws need to be drilled and an screw extractor used,, i would recommend removing the cover and using a drill press...

 

[tall terry]

I'm with hillcat,,, my guess would be you don't have the experience with the impact driver, to use it effectively..
it must be inserted squarely, and firmly preloaded in the direction of loosening,,, if not,, the tool won't work as designed..
congrats on no drilling