Some comments on gearboxes:
The new MTDs seems to be the same gearbox they have used for many years. Not so thick aluminum with a small brass gear. For most models 5hp up to 13 on the standard models I’ve seen they use the same components. I have not seen them but people have mentioned MTD pro or commercial models with a CI gearboxes. They are probably ok.
Ariens has a few versions of aluminum gearbox. The basic gearbox seems to be essentially the same they have used for many years. The newer implementations use a gear which is approximately the same size as the MTD gear. Prior to using that gear they had a similar size gear that had a side section about ¼ inch which would add rigidity. That side section held the gear shear pin. Pre-Briggs 5-7hp Simplicity machines used the same style of gear. The old Ariens and Simplicity seemed to be a better gear than MTD and Ariens currently use.
Ariens has introduced the XS aluminum gearbox which is much bigger than their basic gearbox and seems to be thick aluminum. I have not seen one of the gears yet but would think it’s bigger than in their basic aluminum gearbox. The Toro gearbox seems to be about the same as an XS gearbox, i.e. aluminum size and rigidity. The gears, given the case size, are probably close in size.
Ariens CI gearbox uses the same gear as in the XS gearbox so what is the advantage? From what I’ve heard and read over time cast gearboxes are not better for long term wear. Their advantage is breakage. The cast gearbox can take a bigger hit say from something wedging the augers just right to not shear the pins and transfer all the force to the gearbox.
That would make an XS gearbox as good for long term wear as a CI gearbox. The case gearbox’s value is reducing catastrophic failure. Given that total failure is rare a CI gearbox is not so much of an advantage.
Most of the time when something gets tangled in the augers you know and can stop before things go too far. For bigger problems the machine stalls and there is no damage. For still bigger problems the pin shears. Past that is gearbox damage.
All in all it’s a rare thing for something to damage a gearbox. If you walk around your area a few times before the snow season a few times to pickup stones and branches you greatly reduce chances for a problem. If you remember you have a door mat, toys in the yard and paper delivery you won’t suck them in.
Overall there is not much advantage to a cast gearbox for the average person. It’s not like 20% Russian Roulette. Given a slight amount of preseason prep a homeowner will probably never scoop in something that will nuke a gearbox. In commercial service where the machine would clear places they the operator is not familiar the chances are higher of scooping in something that will be a problem. Also say for a company that has a machine for lot clearing. The employee will be using a company machine and not so careful so a CI would be useful here also.
For wear differences:
MTD and Murray are on the low end. Their design has been the same for years. Given that the same gearbox is designed and used on their big machines and works that gearbox in 5 through 10 should be plenty strong for those machines. Outside of a failure and with proper use and even minimal maintenance those gearboxes will easily last for 20 years. I’ve never seen a worn MTD gearbox, only broken gearboxes.
Toro and Ariens aluminum gearboxes are big and strong gearboxes and should outperform MTD and Murray but the difference or advantage is in long term wear >20 years and ability to sustain a bigger gearbox hit. Seeing that the lesser gearboxes and last for 20 years a stronger gearbox is of questionable advantage.
The unknown:
What is the quality of the gear and worm? Over the years I’ve never seen a detail spec of these components. MTD and current Ariens low end aluminum gearboxes have about the same gear. What are they both made of? What are the drive worms made of? Drive worms seem to be some sort of steel and never the problem in wear. The gears wear out faster. On catastrophic failures gears break, teeth chip or smear but the worms usually survive. Worms sometimes deform but can be brought back with filing and used again.
The upshot is gearboxes are not so important in 10hp and below machines for the average person. An aluminum gearbox would be fine. As a qualifier Yamaha use aluminum.
