The dreaded moaning that comes from this transaxle is common enough. The transaxles on these tend to pack with grass on the top and side- keeping heat in rather than allowing the fan to cool. The oil inside deteriorates and won't hydraulically work plus can damage pump parts inside. With the amount of hours on your unit and use that it has seen, it may just be done. Some find improvement by changing the transaxle oil , which requires removal of the transaxle to do so. You will find several posts on the forum on this. Additionally, externally, enough wear may exist in the linkage so that your pedal doesn't quite actuate end to end. The traction belt itself may be worn or glazed along with the problems on the idler pulleys for the belt. Things to watch over, but again the noise is usually from inside. Infact, while the deck is off- clean the grass from around the transaxle and check the belt and pulleys from below.
To reinstall your deck, put the rear clips in first, the pull the deck so you can attache the center- finally the front.

OP - and if you succeed in resurrecting that machine, get a source of compressed air or an electric leaf blower to blast all that trash and grass clippings off the tranny, underside and deck top after each use. Such will help in extending the life of any riding mower.

thinking it is kaput. May just leave the deck off & drag with it being lighter may not stress the machine as much and last a while longer. Maybe can sell the deck with its new spindles in it.

Thinking of a new one any thoughts on a different brand or maybe diesel, ? Thinking of more horses and cut too. I am retireing in Jan so will have more time to take care of it better. A lil older & wizer?? ( I hope)

If you still intend to drag that horse pasture the same way for another 10 years or so, just make sure you get a machine rated for ground engagement - hydro drive or gear drive, used or new. Then you will be able to pull those heavier loads without fear of damaging the unit... :)

Until you actually change out the old oil, you don't know if it is kaput or not.
In any hydraulic system....healthy oil is the first order of business to address in the system operation.
Hydraulics (and hydrostatic drives) are not applications where the oil just "lubricates" machine parts while the parts do their work!! It is much more complex than simple lubrication of moving parts.
In hydraulics.......the oil itself is the main part that actually transmits power. When the oil becomes worn out and degraded...........it begins to foam and aerate. The foamy, aerated oil is incapable of supporting the hydraulic principles that the hydrostatic drive system is based upon.
Using the machine in its present condition for dragging (minus the deck) is NOT going to be any less strenuous on the tranny. Dragging presents a CONSTANT load the tranny must deal with. The weight of the deck is only a momentary load that that becomes insignificant once the tractor has gotten into motion. The strain of dragging, on the other hand, is more akin to climbing a long hill or incline.....that has no crest.
Removing the transaxle to drain it might seem like a daunting task for someone without experience, but it is a very "do-able" DIY project and has saved many a machine from being disposed of.
Of course if you just want to buy a new tractor, you can call it a "retirement gift" from you to you.
:^)

Mownie as usual is concise in his explanation. The service could work out. However, L120s with a thousand hours of use don't have lots more left to give- especially being used on the rough side.. If you wished to give it a try yourself, $$ wise, you won't be out much. If someone approached me do it for them, with the hours and use- I'd suggest it may not worth the gamble tho. Enjoy, you only retire 2-3 times in life- make it a good one!

I see yer point mounie didnt think of it that way (obviously) & what the heck I do have 2 crescent wrenches & a pipe to extend them, a hammer too somewhere :)

***" I do have 2 crescent wrenches & a pipe to extend them, a hammer too somewhere :)"***
Shudder & cringe.
Happy New Year :^)

Mownie: Sad part of that is--a lot of do-it-yerself-fixers don't have many more tools than that!
I worked with a guy who tried using a half-inch air drive torque wrench to turn the engine, to try to get it running!
You probably know how that turned out! BANG/flop/wide eyes/question marks/ angry boss! And, crankshaft with no threads! Hexx in camp, that day!

Thanks all for the great info. I removed the Transaxel drained it and refilled it, etc etc.. It wasn't all that hard to do but I have to admit a very large & strong & mechanicly inclined friend happened by, and made the work much easier. Would have been a hassle to hold it up to take out and put the bolts back in except he could hold the unit in place with one hand and insert bolts on his side while I did the other.. Took longer to drain & refill than the removal & replacement. Machine works much better with only a slight noise when in motion. I dont remember if it had the nose when newer much too many hours ago.. Has much more speed & power & maintains it now too.

There you go Mac. Good job! (and a round of applause for mr. mac, please folks)
Enjoy your retirement.

If you would take on a job like this, should you just drain the oil or should you drain the oil and the use a "very" light oil to flush and disolve the sludge in the transmission before replacing with the operation oil

There will not be any appreciable sludge build up to contend with.
The real issue in hydrostats is not due to any build up or collection of debris.................the issue is nearly complete degradation of the oil itself.
Essentially the oil loses practically all of its vital additives that make oil behave properly where the task is hydraulic work.
The main thing that goes wrong with the oil is that it loses its anti-foaming properties.
Once the anti-foaming (anti-aeration) properties are gone, the oil will begin to entrain large amounts of air in the form of micro bubbles.
The air entrained in the oil absolutely squashes the hydraulic principles that the hydrostat works on.
If there are any concerns that you might not be getting enough old oil out with a single draining, then repeat the job in about 2 or 3 years.
Flushing will not really help because the very little oil that DOES NOT drain out is sequestered inside the pump and motor anyway, so it's there until you operate the transmission again.
I do recommend that the tranny be left to drain at least overnight and even a week in cold temperatures would not be a bad idea.