How do I remove the old chuk from my 18v drill. I can't tell but it looks like a allen bolt? Would it be a left or right hand turn to remove it? Thanks

open the chuck jaws right up
down the center of the chuck you will see either a philips screw head or a hex head for allen key
hold the shaft at the base of the chuck to stop it from turning and undo the screw in the chuck in a right hand direction ( it is a left hand thread) when you have that out , still holding the shaft turn the chuck in the left hand direction ( normal thread ) and screw the chuck off
to assist in undoing the chuck do it up so that the jaws come out a bit
place something between the 3 jaws to act as a lever or use an allen key in the chuck done it tight and use that as a lever to undo the chuck
the secret is the lh thread screw in side the chuck which stops it from undoing when the drill is in reverse

This could be caused by several things.
open it all the way and check the claws for damage or something stuck in them
there should be an allen head bolt inside at the base...check to see if this is loose....it is a left hand thread, if it is tight and the problem is damaged claws then take out this allen bolt, tighten a large allen key in jaws (or grab the outside with visegrips) and give it a sharp snap to the right to remove the end and replace it.

The chuck has a left hand threaded screw inside. Turn to the right when removing the screw. Once the screw is removed you can remove the chuck by turning it to the left as it has standard, right hand threads. It is easiest to insert a large, L shaped allen wrench into the chuck, tighten the chuck, and hit the wrench with a hammer to spin the chuck off.

There is no loctite on the chuck threads, only blue loctite on the reverse screw. This is how I remove chucks.

Remove the REVERSE-THREAD screw at the bottom of the chuck. Set the clutch collar to the highest setting, and set the gear to the slowest setting on the transmission. Remove the power source! Get the biggest allen wrench you can fit in the end of the chuck(the shortest leg) and tighten the chuck down around it, allowing the jaws to rest and tighten on the flats of the wrench. Lay the drill on its side(chuck toward you, handle to the left, and allen wrench to the left, horizontal to the deck). Then with a hammer(soft hammer if you care about the allen wrench) quickly and deliberately hit the allen wrench in an attempt to cause the allen wrench to spin counter clockwise. Let me know if this works for you!

They torque them on there so it won't fall off under hammer use, they never know what you will be doing so they don't take chances. You will have a tough time getting that thing off, why do you want it off anyway?

The screw mentioned in solution number one is a left hand thread once you have removed it use an allen hey in the hole the screw came out of as if undoing a normal right hand thread a scarp blow with a hammer may be neccesary. then do the opposite when installing new chuck

You must remove the inner chuck retaining bolt first, it is a torx screw and is left hand thread. once you have this screw out, get yourself a 1/2" allen key (the L kind). Chuck the short end in the chuck to grip it, use a mallet to hit on the long end (this will unthread the chuck). The spindle thread is regular Right hand thread. It may take a few good hits to knock it loose but it will come off.

Open up the old chuck all the way and there is a screw down in the middle of the chuck, unless it is missing. The screw is left-handed threads. Remove the screw. Take a large allen wrench. Tighten down in the old chuck. The chuck is right handed threads. Lay the tool down on its side. Take a hammer and hit the other end of the allen wrench several times until the chuck comes off (some of them are on very tight). If it doesn't come off, then spray WD-40 down inside the chuck and let it sit overnight or for a few hours and then try it again.
Good luck!
Don-www.toolsandmachinery.com

The only way is with a special chuk key , and is not available to customers, if you still want to replace by yourself, you can by the whole gear case cover assemble that cames with the new chuck, but is is expensive.

position the drill to speed one & drill mode.u need a allen key then clamp it the chuck jaw close & tight. hit the allen key with hammer counter clockwise until its loosen. may have to do it any several times.