Likely causes could be a badly worn drive belt, low oil level in the transaxel or a problem inside. I assume that the engine power is consistant? The Drive controls themselves feel normal?

Lost or broken spring on drive belt tensioner pulley.

Broken or failed tensioner pulley on drive belt.

Cooling fan on top of transaxle packed with dirt and trans overheated.

tomplum: the oil level is between the add and full, close to the full mark with the engine cold and not running. Is this the same oil that is used in the transaxel? The drive belt is the original. Engine power is consistant. Drive controls feel normal.

justalurker: the cooling fan IS packed with dirt, not the fins themselves, but the top of it. The tensioner pulley, is this the same as the idler v-groove 910" offset or perhaps the pulley idler flat?

By removing the deck, will I have access to change the drive belt and clean the fan? I look at the tractor and think, how am I ever going to get access to these areas? Do the gas tank and/or tire need to be removed?

Roseazalea - before you do anything further, get/ read the owner's manual for this tractor.
After reading, decide whether you want to try fixing yerself or take it to a shop (or sears).before you tear it apart, you need to have a better idea of what's really wrong. The problem you describe is likely in your transmission (ground drive), not your engine or engine oil. the tranny has it's own separate lubrication/reservoir - some models can be checked/replenished, other models not. your manual will tell you.
When you feel you have more accurately defined the problem or fault, post back with details and you will get more help here.

A Sears GT6500 is a garden tractor and will have either a Tuff-Torq or Hydro-Gear transaxle.

IIRC the TT trans can be drained and refilled while the Hydro-Gear can't or is not easy to do.

I think the OP's problem is in the drive belt or idler pulleys and/or tensioner pulley.

The manual is the place to start especially since they can be downloaded for free if the OP doesn't have one.

The oil level of the engine would be a seperate issue. It sounds as though that you weren't keen on doing advanced maintenance yourself. Forgive me if I am wrong. I just wanted to point out that you could be dealing with something simple, or if luck wasn't with you it could be a bigger deal. The 917# from below the seat would be helpful for more insight. It is good you now know about keeping the cooling fan and transaxle clean to reduce overheating. Simply cleaning that won't help your immediate problem however.

Thanks for all the advice thus far. You are correct, I am not familiar with engines. Gotta start somewhere though right? The model number is 917.276920. Replacing the drive belt may fix the problem? How simple is it to replace the drive belt? It is a hydro transaxle.

You need the manual for your tractor. It will either show you the procedure to replace the drive belt or have a parts listing showing you the layout and idler and tensioner pulleys.

You may have a bad belt or a bad idler pulley(s) or a bad tensioner or pulley.

It can be a PITA to replace a belt cause you have to remove the mowing deck and you're working upside down. You may have to remove some of the steering gear to get the old belt off and the new belt in. There are a number of idler pulleys and belt guides.

If you have the knowledge and the tools then the job is simple. If you don't then you'll be trailering your tractor to a shop and paying them to correct whatever additional problems you add.

Here's the parts diagram of the drive belt...

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If you feel that you can pull and reinstall the deck , you should be able to replace the belt. We can walk through it. Do a visual inspection first. The traction belt is not very wide-close to 1/2 inch. They can wear thin. Know that the sides of the belt do the actual driving, so if the belt was worn thin or is glazed- it will affect the grip. Set the park brake so you can inspect the pulleys. A peek at the idler pulleys for turning freely and wear + the front drive pulley (they sometimes split or get badly glazed) is a good idea. The part # is 165813 and any AYP/ EHP dealer can get it for you. It isn't the most common, but should come from the distributor.

Here is a link that might be useful: Sears parts

Here's a link to the tractor manual... click here to download manual

The drive belt replacement procedure is covered in the manual.

justalurker and tomplum:
You are both so helpful. Thanks for the diagrams and links. I didn't realize the operator's manual would tell me how to change the belt. Page 27 There is even a belt installation guide decal on the bottom of left footrest so when one is laying on ones back it can be referred to. Does sound complex, but I will give it a shot. All 100 lbs. of me was able to install the deck when I first got the tractor, and remove it a few times for blade sharpening. No fun, but it will save me $$$. Being able to read will help alot. Have to order the belt, (thanks for the part number). You guys are smart. I will not know if this solves the problem until spring though. Thanks so much for your time and advice here. I'll post back if I need rescued :)

Can you tell by this image if the belt is worn?

Can you tell from this image if the belt needs replaced?
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I received the replacement belt... $60!!! Thought about going generic for $25 but decided Craftsman is a wiser choice. It was really filthy under the tractor. Always used a leaf blower to clean it up after every use, but never got underneath it in the four years I've owned it...hmmm could that have been the problem? I know you already said that just cleaning it won't fix it, Tomplum. Ok, it still doesn't look clean, but I vacuumed all the loose debris, and since I use a mulching blade and do a lot of oak leaves in the fall, there was tons of dirt/leaf cuttings/grass cuttings caked in places. What's your thoughts?

Leaves and such can easily get in the V section of the pulleys and cause the belt to polish or burn.

Sticks and stuff can get into the tensioner mechanism or bind an idler pulley and accelerate bearing problems.

An exposed belt drive system screams out for routine cleaning and inspection which that should be done after every use.

The OEM belt is the smart call... you KNOW it is the correct belt and not an aftermarket one that's close

I need help to identify the transaxel I have in a 1997 Toro Wheel Horse 269H Model 72102 tractor. I recently installed a new Courage 20Hp engine and clutch with new belts.That Cost about $1400 and now eveything works well except the transaxel began losing power after it runs about 30 minutes and gets hot. I tried to find a drain plug to drain and replace the old transaxel oil but can't locate one on the unit nor can i locate a schematic on line or in my owners manual. I think that is why they refer to this transaxel as one not to be opened.
Anyone know some way to properly drain the transaxel and/or suggest help to find an internet site that describes what I can do to fix my problem. My Toro dealer says my tractor is too old to mess with and I should spend $5000 for new one. I like the tractor and have a snowplow and other items I use with it. It loks like it is new and garage kept,
Help
DenvilleDave

Basically, the best and ultimately most effective way to do this job is to remove the transaxle assembly from the tractor and place the unit upside down over a suitable catch pan/bucket and allow it to drain like that for at least a day, or even better.............a week.
If you can do the work yourself it is not too bad a deal.
Been done many times and saved many a transaxle from an untimely demise.
The statements from your dealer pretty much outline one of the mindsets of a price point driven industry wherein there are myriad strategies to cut costs of product units to entice buyers. The downside of this is the products end up with built-in pit falls that ensure you need to repeat the cycle of "buy, use, dispose, buy again".
By claiming "no service needed", it is convenient to also claim later that the unit cannot be repaired, thus nudging one to buy a new unit.

You can do an in depth search in this forum to learn of the many instances where a complete transaxle has been removed and drained/refilled with excellent results for the effort.
Should you decide to embark on this, be sure you take a huge number of digital photos of everything you do, before you do it. that way you can refer to the pics and everything will be good when you reassemble.