Mold and grass buildup on mower deck underside

   / Mold and grass buildup on mower deck underside #12  
That's what pressure washers are for. Be sure to grease the spindles afterwards to shove out any water than might have gotten by a worn seal.

My gravel driveway did a pretty good job of cleaning off the underside.
 
   / Mold and grass buildup on mower deck underside #13  
The issue with those are, they will contaminate your spindles with water and displace the grease of you don't greas them after you do it. Nice design that has underisreable after effects. My wife's ZTR came with them and I've never used them.
I removed the one on my new ZTR. I think it's sole purpose is a trip hazard.
 
   / Mold and grass buildup on mower deck underside #14  
The spindles with a zerk fitting on them don't grease the
bearings the bearings are sealed you need to take the spindle
out lift the seal on the bearings and add grease


willy
 
   / Mold and grass buildup on mower deck underside #15  
I just pick up the entire mower, deck and all with a short chain or strap attached to the front axle or a convenient point and hoist it up woth one of my tractor's FEL and clean it.
I've been doing the same off and on for years, not as religiously as I should, but there are only so many hours in each week. I've taken to jamming a big wood block (LVL section) under the rig after lifting, ever since having had a hose failure on my loader while lifting a brush hog / rotary mower deck to clean under it.

You'd think a loader probably bleeds down relatively slowly when a hose fails, but nope... mine came crashing down like a sack of bricks dropped from a window. Even relatively young and athletic, I was maybe 40 when that happened, there's not a snowball's chance in hell that I'd have been able to get out from under that rig as fast as it came crashing down. Thankfully I was 20 feet away, turning on the hose, when it happened.
 
   / Mold and grass buildup on mower deck underside #16  
I try my best to only cut dry grass, but even dry grass has a decent amount of moisture in it. Tried the deck wash part on deck, really didn't work. I found myself lifting and fast releasing so deck would hit ground hard to dislodge clumps with water running. Easier and cleaner to raise deck and scrape with putty knife.
 
   / Mold and grass buildup on mower deck underside #17  
As mentioned, there's no magic. I've tried repainting, Fluid Film, Lanox, spray oils, etc. Our grass can be pretty juicy even though it seems dry. I don't take very good care of my decks.

Cleaning is done using one of two methods. One is with a long handle scraper with jackstands under the RFM. The other is with the RFM raised and the tractor parked with the front wheels down over a steep bank, then using a pressure washer.

Recently the DeWalt 20V pressure washer was pressed into service following some wet grass mowing sessions. The mower did an outstanding job, and when the underside of the deck was hit with the DeWalt, big clumps of mushy grass fell right off like big dark green wads of soaked toilet paper. SPLAT!!
 
   / Mold and grass buildup on mower deck underside #18  
I changed the oil in my Hustler today, and took a look around while under there. Clean as a whistle. It's never once had the deck cleaned
IMG20250527180104.jpg
 
   / Mold and grass buildup on mower deck underside #19  
I had to mow up north. It was tall and wet, no choice. It’s been raining so much there this year, I had to cut on a day that there was a break in rain. Looks like my next trip will be cleaning the crap stuck under the deck. I probably should have used the finish mower behind the T25 instead of the JD. It was slow going.
 

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   / Mold and grass buildup on mower deck underside #20  
Nothing you can apply to the underside of any deck, fabricated or stamped (I prefer a fabricated deck as it's thicker gage material will stay on very long, no matter what the mainfacturer of the product claims, IOW they are all just a waste of money.

Your best bet is to clean it regularly. I never remove the deck, I just pick up the entire mower, deck and all with a short chain or strap attached to the front axle or a convenient point and hoist it up woth one of my tractor's FEL and clean it. Somethimes I use the pressure washer, sometimes a putty knife (depends on how thick the 'cud' is on the underside of the deck) and call it good, but when I clean it, I always regrease the spindles afterwards. It's a good time to check the blades for wear or divots as well. When I hoist mine up I don't stand the vertical, just hoist them enough to access the underside of the deck easily.

How I do it, your mileage may vary.

One thing I always do is they get cleaned prior to winter storage as that 'cud' promotes corrosion over the off season... and moldy wet cud stinks anyway.
Keep a short chain routed to the front axle of my ZTR axle. Use a chain hook welded to the FEL bucket and pickup front of mower. Use an old butcher knife and putty knife and scrape deck every 2 months or when blades changed.
 

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