hydrostic drive will not pull uphill

Is it the tires slipping? If not, transmission oil level, transmission oil filter. Maybe it wouldn't hurt to change the transmission fluid.

Sounds like that piece of crap John Deere L120 I had. The transmssions are not servicable by the average person. They are good for maybe 300 hours if put under much of a load. The better ones recommend changing around 50 hours and every 200 hours after or something like that.

If it is easy to change the transmission fluid I would give that a try. Could be the fan on it is bad if it gets too hot they will not pull.

Too bad that the OP < home-moaners club > didn't think to post the year & make & model ...

ps : after 5 years of owning a Kia Rondo I only recently discovered that the auto-trans is a sealed unit - no dipstick - ... except me of course ! .. and NO it's not CVT ! ... 6-speed auto. .. profoundly ashamed .. I check my lawn tractor's tranny more than my car .. John T.

Some cut.

Blame that on the manufacturers. Most things are a lot more reliable than in the past. No points and condensers, or carburetors to mess with. Why look under the hood? My brother and I recently bought a Massey Ferguson GC 1725 compact tractor for our farmstead. It's big enough to handle a small front loader and has a mid mount mower.

Did you check the oil?