Caution: Wear eye protection at all times while attempted to do this work. Do not hold sockets or punches with your hands while hitting on them with a hammer. Use the appropriate punch holding tool, or locking pliers to securely hold punches or sockets. When using a puller, make sure you lubricate the driving screw, and do not use an impact gun to tighten the puller shaft! In my many years of experience an impact gun, and puller are never a good idea to use together.
I just want to say a word about my use of impact sockets as punches on some steps of this Instructable. I have been a technician for large vehicles well over 13 years now. I am well aware that sockets are made for removing fasteners. If you are fortunate enough to have a set of bearing removal tools you should use it. I, on the other hand, do not have the sizes in my normal inventory of tools for work this small. Therefore, I thought I would use the backyard mechanic way of driving out shafts using sockets. I feel that impact sockets are safer than regular chrome sockets, because the metal used on impact sockets is more malleable. No matter what method you have at your disposal, you must and always should use eye protection whenever using a hammer that is intended to contact other metal objects, such as the sockets or punches used here.
Step 1: Removing M18 Nut With Impact Gun
Secure the blade holder end of the spindle in a vise and remove the lock-nut using an impact wrench. Once the nut is removed, you can pull off the pulley assembly. You may need to use a large bearing separator to drive the shaft of the spindle out of the center of the pulley, to avoid distorting the pulley.
Do not hit the bottom of the pulley with a hammer, you will bend it.
Step 2: Remove the Woodruff Key
Using a punch and hammer, carefully drive the woodruff key out of the shaft. It may be easier to lay the shaft horizontally on a hard surface with the woodruff key facing up, then tapping one side of the key into the shaft to get the key to roll out of the concave hole.
Step 3: Drive the Shaft Out Using a Puller
Using a 3 jaw puller, you need to put pressure on the center of the shaft. The shaft may be very difficult to press out using a puller. Do not be temped to use an impact gun; instead, just hit the top of the puller with one shot from a hammer, and continue tighten the drive screw on the puller. When the shaft gets difficult to turn, just hit the top of the drive screw with the hammer, again. Each time the screw is hit, the puller will be easier to turn.
Step 4: Using a Hammer Only to Drive Out the Shaft
Please note: I do not recommend this method, unless you are certain the shaft is not stuck in the bearings. Driving the shaft out using a large hammer can potentially crack the housing where the bolts hold it into the mower deck.
If you do not have a puller, or you cannot keep the puller on the housing as the shaft gets pressed further out, you can use an impact socket and a hammer to drive the shaft out. Make sure you use something that is smaller than the threaded end of the shaft, so you do not damage the threads. Never hit the end of the shaft with a hammer!
Step 5: Removing the Lower Bearing.
The lower bearing (on the side that the blade is mounted) can be driven out with a punch from the pulley side of the housing. There is a spacer between the bearings that can be easily moved out of the way so the bearing can be driven out. Notice the spacer that is between the bearings.
Step 6: Removing Upper Bearing
The upper bearing is held in place using two circlips (or snap-rings). You only need to remove the clip/ring on the end of the housing. You may need to tap the clip around the perimeter with a hammer and punch and even use penetrating oil to get the clip to come out. After the clip is removed, turn the housing over, and just tap the bearing out using a socket or punch.
Step 7: Clean Out the Housing
Take a moment to enjoy your handy work, and toss the old bearings. Clean out the housing, to prepare for the new bearings. If necessary use some emery paper to remove any large rust buildup, where the bearings will sit.
Notice the internal clip/ring inside the housing. You should not remove that ring, and it should not be damaged or missing.
Step 8: Pressing in the New Lower Bearing
Using the vice, line up the bearing, and carefully tighten it in the vise to make sure it goes into the housing squarely. When the bearing can no longer go in any further with the vice, remove the housing from the vice, and using a small hammer, and socket that fits over the outer perimeter of the bearing, gently tap the bearing until it bottoms on the internal ring/clip.
Re-install the external ring/clip, and make sure it is completely in the groove all the way around the housing.
Step 9: Pressing in the New Upper Bearing (side With the Pulley)
Make sure you install the spacer first!
Line up the new bearing in the housing, and you can use the method as before with the vise to press the bearing in. Don't worry about the spacer, you will be able to line it back up before you drive the spindle shaft back into the assembly.
Step 10: Driving the Spindle Shaft Into the New Bearings
Make sure the spindle shaft is clean, and all rust is removed.
Apply a light coat of never-seize to the shaft. Make sure the bushing is lined up behind the opening of the bearing, and then tap the shaft into the first bearing, so that it starts to go into the bushing. You can then use the press, and press the shaft most of the way into the new bearings. Eventually you will have the vise touching both ends of the shaft, and will have to go onto the next step.
Step 11: Driving the Housing Further Onto the Shaft
With the blade end of the shaft on a sturdy surface, and using a socket that contacts the inner metal portion of the bearing, drive the housing the rest of the way onto the shaft.
Make sure that you use a socket that is just big enough to not contact the threads on the end of the shaft.
Step 12: Install the Woodruff Key
Apply some never-seize to the woodruff key, and gently tap it back into it's hole. The key should be parallel with the shaft!
Step 13: Installing the Pulley
Using the same socket at the previous step to drive the housing onto the shaft, gently tap the pulley all the way onto the shaft, and install the Lock-Nut. Do not over-tighten the lock-nut. It is designed to be very hard to remove, and install so it does not come off in operation.