The most-embarrasing broken "tool" I've dealt with recently is the "tool" I use to mow my lawn--a "box store" John Deere D170. Not big or sturdy enough to be a garden tractor, just a riding lawn mower/snow blower.
I'm riding along cuttin' grass. And then...no forward motion. No reverse, either. I tow the thing back to the shop, lift it up...broken belt between engine and transaxle. It's really worn, but it's also never been replaced since I've owned it, and it's probably the original belt at 250 hours, so I figure that's normal. I buy a belt (in stock at the JD dealership) and get it installed. I have approximately 1/4 the speed I'd had before. Which gets me to thinking, when I first bought this mower, it'd climb out of the ditch in front of my house with no problem. And now I gotta sneak out at an angle, with a running start 'cause it won't climb the grade any more. And it hasn't been properly fast for a month or more.
Online research leads me to discover it's got the hated, light-duty "Tuff-Torq K46" transaxle, famous all over the internet for failure. Metal shavings everywhere, no user-serviceable filter, no drain plug. Every web site I visit has the same complaints about the K46. The only "happy endings" are a couple of cases where folks drain the original fluid by taking the case halves apart, cleaning the internal filter screen, and re-filling with 5W-50 synthetic oil.
I remove the transaxle, pop the bottom cover off. I drill and tap it for the two drain plugs that Tuff Torq should have installed to begin with. The magnets are covered in fuzz, but it really doesn't look as horrible as I expected. Almost nothing on the filter screen. Put the case half back on...fill with Mobil1...reinstall in the mower. And I have about 1/4 the speed I should have.
Now I'm pissed. The transaxle comes out AGAIN. More "internet research" leads me to a Surplus Store in Nebraska that's blowing-out K57R transaxles for about $300 shipped to my door. (The price has since gone up--
today they're $340 + shipping.) This is a Tuff-Torq transaxle intended for a Husqvarna, but it should physically fit my JD. I have to swap the longer JD axle shafts into the new transaxle, the Husqvarna axles are too short. And the motor spins the wrong direction, but it's reversible by flipping a wedge-plate upside down. And the levers for forward/backward, and brake are wrong for the JD, so I have to swap levers. And pulley. All that stuff comes off my weakling K46, and slides right onto the new K57R. Turns out, the K57 is built using the case halves of a K46, there's just some extra hydraulic circuitry inside, and better oil pumping/oil filtering. And since I have to open the case halves to do all this, I drill and tap the two drain plug holes that Tuff Torq should have already done. Fill it up with Mobil1 5W50.
I install my K57R...make one circle in the driveway, and have about 1/4 the speed I should have.
This time, I reach under the thing, and my new transaxle belt is so hot I can't hold onto it.
I go to the local hardware store, buy a bigass tension spring. I drill a little hole in the frame to attach one end of the tension spring, and hook the other end around the belt tensioner keeping the original belt tension spring as-is.
Full speed ahead. Climbs out of the ditch with no problem.
I spent $325+ and wasted days of effort removing, cleaning, installing, removing again, and finally swapping transaxles based on the terrible internet reputation of the K46, when I actually needed a new belt and a $7 tension spring because the JD spring relaxed in service.
The upside, I guess, is that if blow-up the K57R, I can swap the axle shafts, levers, and pulley back onto the original K46 and reinstall it.
I'm a moron for not checking belt tension when I installed the new belt.