Inquire and ye shall learn: Ok so I googled it and AI says this:
AI Overview
The openings near the spindles on a Cub Cadet ZTR 50 mower deck are designed to allow air to flow through, which helps create a vacuum for better grass lift and a more even cut,
according to a forum discussion on Only Cub Cadets. This airflow is crucial for the mower's cutting performance.
So, to answer the question for the OP, should I close up these holes? I think the answer is no, according to what AI says. Now that raises another question: why do some of their decks have holes and others don't? Also, on the decks without the holes, what is the quality of the cut, does it leave any uncut or unevenly cut grass?
My mower was purchased new a lot of years ago from Home Depot, and when I first got it, the cut was perfect. It has been a great machine, just now coming on 350 hours, and this since
I think 2009 or so. I have replaced the belts, blades some of the tires, touched up the paint, and just recently recovered the seat. All of these things are time/age-related as opposed to high-hour usage, as I have several mowers to work with.
I will try, as I mentioned earlier, to keep the top of the mower deck cleaned off several times while mowing acreage to see if this improves the cut. I have read on lawn mower forums that this problem is very common on many types/ brands of mowers. The experts there usually blame unlevel decks, belt slippage, badly worn pulleys, improper use or installation of blades or damaged/ dull blades, bad spindle bearings causing blade tip speed slow down, etc. All of these things I have checked for on my mower. Some of the experts there say that some mower decks are NOT made to be used with HIGH LIFT blades. I do not remember what the original blades that came on my mower were. But as best as I can remember, I don't think they had the high back 'wings' on the back of the blades. Has anyone else come across this as a problem on your machine? I have been trying to find a Cub Cadet original blade part number and get a set of those blades to try. So far no luck.