Comparing repairs on 2010 Series 860 self-propelled vs buying new mower

[GrowinWeeds]

Full model is 12AI869F011. Cost $303 in 2010. If anyone owned this age & (similar) model Troy-bilt, I'd like to hear your experiences, once it got this old (11 yrs). Assuming you take good care of equipment.
Since I've never replaced a drive belt, nor worked self-propelled mower transmissions, I'm cautious about what else might need to be replaced, when I open it up, or is common to wear out on this old a Troy-Bilt walk behind.
I'm not worried about doing the mechanical work. I've done total auto engine rebuilds since age 16 & repaired almost every appliance. For looooong time. One was a 68 Camaro - metalic blue. Wish I had it & 50 yrs back.

I don't know what ELSE commonly goes bad on this generation / similar model Troy-Bilt self-propelled transmissions, various bearings, etc., once you open them up to do "simple belt replacement."
Not sure if the transmission lasting this long & working fine - till belt broke - is already long past most needing a new tranny, or scraping the mower. I don't have "new equipment-itis." But don't believe in throwing good money after bad.

Should mention it has a large rusted out hole in deck, where a piece of plastic butted against the deck bottom (bad design - obvious what caused rust out in one spot, on a slope). Rest of deck seems very solid, as I regularly cleaned it.
I'm confident I can patch the hole w/ even heavier gauge, rust resistant metal. I'd paint w/ rust preventing coating before putting patch on, then fill any gaps w/ silicone or high performance caulking, to keep out moisture & debris.

The Briggs engine 775 / 800, model 110000, 175cc, 7.75 ft-lb is in fantastic shape. Still starts easy. Doesn't use oil - at all & I changed it at start & end of mowing season. I always use Star Tron. It has plenty of power, even in tall, wet grass (when it rains daily for 2+ wks).
It also needs a couple of cables. Surprised they broke, since it's always garaged. Local prices on them aren't too much.
The parts it needs aren't that much (compared to a good new mower). It's other parts likely to need replacing soon - I'm not aware of - that's the real concern.

 

[GrowinWeeds]

Thanks for helpful... wait, there aren't any replies.
Well, this should make you scratch your head. After draining oil (thru filler tube) & gas, tried to figure exactly why the worst rust was in one spot.

This TB walk behind self-propelled model has a round, flat bottomed plastic pan (roughly 8 - 10" dia.) that covers the bottom of engine. Part of it butts against the plastic cover for self-propelled belt, some of the rear pulley, etc. There's a 2nd plastic "bowl" that's covered by the 1st one described. No idea what the need for the 2nd (inner) bowl is, other than to trap moisture.

When I removed the outer plastic pan, it was partly full of dirt & ants w/ larvae. Part of that dirt was against part of the steel deck.
But the pan nor ant "nest" went up as far as the completely rusted out hole was. Part of the totally missing hole wasn't covered w/ anything to support more ant nest. There was no grass clumped up at that spot.

This mower never sits outside. Once in a long time, it may sit out one night (on concrete) if we're too tired to clean it underneath, & put in the shed. It gets cleaned & put up the next day. No ants in the shed.
One amazing thing is, for at least one mowing - maybe more, the ants were in there & put up w/ that kind of vibration & banging. If you just disturb most ant mounds around here, they move the next day or 2.

It's a highly unusual place for an ant bed, as they have to carry the dirt so far, to place it under the mower. It doesn't give them space to make their nest > a couple inches deep.
Here, their under ground tunnels & chambers are as deep or deeper than a normal shovel would reach, if you push it all the way in the ground.

The only reason I'd consider patching it now (besides $$$ for a "good" mower) is the engine seems perfect. There's ZERO carbon build up, ash or anything on the spark plug - probably 2 yrs old. It almost looks like it was just installed. Maybe I could sell the engine & get something.

There's more metal missing or thinned from rusting than I thought, before pulling the plastic pan off. One end of the big hole, extends almost to the engine's base.
Which means there's nothing to weld or bolt heavy sheet metal to w/o unbolting the engine. Then I'd have to put a solid piece of same thickness metal (or shims) under the engine, to keep it "level."

I don't know if there's enough "solid deck" under & around the engine to keep it stable, so that any metal patch doesn't need to support the engine (that much). Or the method of connecting the patch is strong enough to reduce vibration, caused by missing metal. Just covering the hole w/ fairly thick sheet metal or layers of fiberglass to keep grass UNDER the mower wouldn't be that difficult.
Making it structurally strong is another matter.
I'll have to remove all bubbled up paint around the entire "drainage channel" to see if more metal is weakened - showing rusted pin holes.

 

[dougand3]

Are the engine mounting holes in rusty hole areas? - Can the engine be moved off the vertical axis? If the engine is not stable, the deck has to be welded for strength or a good deck brought in.
Recently, I looked at mowers in $300-$350 range and said no way would I buy one. I'll fix an older mower. Yours is decent quality, esp the Briggs 11 series. I like push mowers - 2005 and older for quality.
Cables will rust internally - squirt some PBlaster or Liquid Wrench to travel down the center cable if they feel restricted at all.
I wouldn't spend any $ on the SP tranny. Internally, it will probably outlast other mower parts. The metal gears to drive wheels are probably fine but the plastic wheel gear will wear. I bet the special geared wheels are NLA.

 

[slomo]

My advice, look for an older Snapper pusher. Snapper hardly never changes anything on their mowers. If they do, that change stays in production for decades. Meaning spare parts are all over and cheap. Your kids kids grand kids will be mowing with it.

10 years of use on that TB mower is all that you might expect out of her.