The drive wheels on a Toro are different than those on other mowers. They use a different size drive gear, less teeth, smaller gear size. Because of that the gear on the wheels are larger. Because of this the alignment between the drive gear and wheel gear has a closer tolerance. Toro’s design for the axle alignment never took this into consideration and the result was that the metal drive gear chewed up the plastic wheel gear. I can’t count the number of wheels I had to replace in and out of warranty. Bulletins had you realign the bearing holders and check wheel axle bolts. Neither were successful at fixing the problem. As a mechanic and sales person my tongue was bleeding many times. This is the reason I never recommend purchasing a steel deck Toro mower, but I did sell many, even after telling customers my concerns, because of the price difference.
Disclaimer, I have been working for Toro dealerships since 1981 and was a strong supporter of all Toro equipment until the last 10 years. Now I pick and choose what I recommend.