Small Engines (Lawn Mowers, etc.): Tractor wont go up hill, proper manuals, tension spring

Question
I Have a John Deere LT180.  The tractors seems to run fine for around 30 to 45 minutes, then the mower won't go up the same hill that it was pulling before.  This only happens in the grass, I can back up and go up my drive and it will make it.  This is not a steep or a big hill. I had the drive belt replaced because the old one was cracked with age.  It has a hydrostatic transmission, but I don't have a clue on how to repair them.  Is there anything I can do before I need to take it to the shop.  
Thanks,
Chad

Answer
Hello Chad:

You can View a Breakdown/IPL of the Engine and Mower at this Site Addy, http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.H... and Enter the Model Numbers (LT280) and Click Find. Then Select your Model from the Search Results Area. Then Select the Sectional File. Then Select the Section of the Mower you Wish to View Online. Select the "Power Train" File. If the Belt is Tight and the Tension Spring is Holding Good Tension on the Drive Belt, then the Transaxle May Require Fluid. On Some of these Hydro Transaxles there is an OEM Tag. Send me the Information Off of This Plate, Please. With this Information, I can Locate the Proper Manuals and Better Assist You. Sometimes you can Remove the Cap (#9) in the "Transaxle" File and Add 1/2 Quart of SAE 30 Engine Oil to the Hydro. If the 1/2 Quart has No Effect, then Add Another 1/2 Quart. If this has No Effect, then there is an Internal Problem with the Hydro. If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Thanks.

Respectfully

John