Great advise on the pin removal ! I too made the blunder of driving a pin too far through the gear and then couldn't rotate it back around to get the pin out. It was my extreme good fortune that the box I was learning on was pretty much a junk one anyway, very rusty inside. I was just tearing it apart for whatever I could possibly salvage. I ended up forcing the shaft back around which bound the end of the pin against the inside of the case, finally broke the pin off near the surface of the gears hub. Made quite a gouge in the gearcase. Wasn't a big deal as the case was beat up on both snouts where the seals go and had a crack in it too. All the boxes I have recently taken apart I have done the "grind the end off" method till the pin is short enough to clear the hole in the shaft. This of course necessitates the complete disassembly of the box to clean out all the metal fragments from the grinding. I'm sure you've had a similar experience. I also had a devil of a time trying to pull the pin with the vise-grip approach. Ended up using end nipper type pliers to pull the pin out. I hadn't thought of putting something inside of the pin so it wouldn't collapse. That is so simple, why didn't I think of it? I also had a thought of drilling a hole in the case to allow the pin to be driven out of the gear and out through the side of the case to remove it. Would have to tap and put a plug in the hole to seal it. I wonder if that would weaken the case enough to cause an issue? I always just figure that the teardown of a box means I need 2 new pins. I have always used the regular duty split pins that I find at the local hardware. I believe that a couple of times the pins I used extended past the surface of the gears hubs by maybe a 1/16" on either side. I remember grinding a pin off a bit because it was longer than needed to fit the gear. The hardware was out of the one I wanted so had to buy the next longer size. I typically grind an extra bit of a bevel on the end that is going in first just to help get it started in the hole too. I thought that it might help align the holes of the shaft and hub if I was off just a smidge too. I'm not sure if having the split in the pin aligned in any particular position makes any difference or not. If you made the split aligned with the length of the shaft then it would be be solid against both surfaces of the gears hub in relation to its rotation. And vice-versa. If that makes any sense? Not exactly sure how to explain it. Probably makes no difference. I also wonder if a smaller diameter split pin could be driven through the one that keeps breaking. Or possibly a piece of some softer metal , a finish nail, a piece of heavy wire? The second pin would prevent the larger pin from distorting from the torque being applied on it. Would have to slather it up with Loc-Tite to make sure it didn't come loose. Maybe a bit of solder on either end? This goes back to the thought of inserting something inside the pin so it won't distort so you can grip it with the vise-grips. Just thoughts.
I wonder if a piece of 1/8" rod would fit inside the roll pin when it is in the gear and shaft. If it would then might be able to put a hook or small flat washer just under 1/4" diameter on a piece about 1-5/8" long and put a thread on the end. Then could insert the piece with the head flush with the roll pin and rotate the shaft half a turn so the thread was now sticking out. Then thread another section of rod on that is threaded - maybe 1/4" threaded rod and then make a U to form a puller to pull the pin out. Not sure how much force would be required on a slow steady pull and whether a piece of 1/8" would have enough strength?? May have to investigate that idea sometime.
I tried putting another roll pin inside a 1/4" pin several years ago when the first roll pin broke on my snow caster. Could not get the double pin started into the gear so I decided to insert the 1/4" pin into the gear and shaft and then try driving in the smaller pin. Bad idea as the 1/4" pin started to drive out the inside and things got really jammed up as I had a pin sticking out both ways and could not remove the smaller one or rotate the shaft to drive the bigger one back. I ended up drilling a hole in the gear case so I could drive the 1/4" pin out from the gear case side and then tapped and threaded the hole for a bolt - can't remember if I used 5/16" or 1/4" UNC but seems to have held and doesn't leak and the case is still intact. Think I loctited the bolt in at the time. I will try and remeber to take a picture of it when I upgrade the gears and shaft in the spring / summer.
I am thinking that when I install the new shaft and gears and use a spirol style pin that will probably fix the roll pin breaking problem. If I can come up with a way of pulling the pin I may use a 1-1/2 long one on the smaller gear so it has support at both sides of the gear from the full hub thickness. I think the gear case design was good at the start of the Tube Frame production run but I imagine from the postings of other members once the roll pin broke it became a weak link for some owners and dealers probably got tired of listening to some of the customers complain that the pin kept breaking on them - just a guess. With the HP increases and larger attachment sizes it appear that Bolens went to a a cast iron gear case with ball bearings and keyed gears on the Medium Frame and large Frame series. Not sure if one could be adapted to a Tube Frame attachment as I think that most of the cast iron gear cases have a 1:1 ratio and the Large Frame PTO's run about half the speed of a Tube Frame.