farmall m tranny

How do I replace this gear its got a chip in it and id like to replace it jus for peace of mind I dont want it to be a problem later on?

Best way by far is to pull the axle housing. Then you can replace the shot gasket and inspect the bearings easier, plus clean the axle housing. Depending on how strong you are, I used to lift them off all the time. Using a couple of dowels for support and alignment. Now days, I have a difficult time even lifting just the axle. A cherry picker works good with a good sturdy stand under the belly of the rear end. You can push the axle out without taking housing off by using the bolt and a block between that and other axle.

There may be a little more to it, but I think you just take that bolt out of it and pull that axle housing off and lift it out.

Thank you both so I can slide jus the axle out and leave the axle housing in place? What bolts do i take out to move just the axle?

the big one in the picture,that holds the bull gear on....dewy

Everyone likes to do things different. I like to remove the axle first and then if needed the axle housing. Remove PTO, bolt and heavy washer from axle inside end. Remove tire and wheel. Remove 4 bolts from retainer at outside end of axle housing. To push axle out I use a 3/4 stud the correct length. Run one end through a nut with 1/4 inch sticking out, weld nut. grind threads off of the 1/4 sticking out so it goes in axle hole without thread damage. Thread another nut up close to other nut. Place a hard washer on. Cut piece of pipe the right length to go between axles and slide over the stud. Handy for removing one axle if a sleeve is added to end of pipe to fit over other axle bolt head. If axle pushes hard all the way out a spacer may need added to pusher. Hold weld nut and turn other to pipe to push. Different or other stuff can be used to push.
Sometimes if not real hard coming out I loosen wheel and slide to end of axle and snug down, then just take a heavy block of wood and hit wheel to bring it out of splines and bearing. With rollers the wheel and tire could be left on and just move axle out enough to clear bull gear splines. But if seal or bearing attention is needed your stuck removing the wheel with less support.
Don't know where your located and if you already found a bull gear. Would be heavy to ship, but I have a couple of good ones.

If your tractor doesn't do much heavy work it would probably be ok as is. If you were tractor pulling or something I would be concerned. Most of the tooth is still there.

So once I remove the bolt holding on the bull gear to the spine of the axle i remove the four bolts holding on the outside of the axle to the housing and jack up the tractor on that side under the axle housing and then I could slide out the axle with the rim and tire still attached? Jus wanted to make sure that was the only bolts that held the axle in place from moving? Thank you

Yes cap with grease fitting is the outer bearing retainer and axle seal mount. has gasket between it and axle housing. Unless you have a lift to support tire and wheel use boards and a couple of pipe for rollers.