Small Engines (Lawn Mowers, etc.): John Deere 180, spider gears, kawasaki engine

Question
I bought a used 180 tractor from a local dealer here about 2 years ago.  The mechanic told me he had replaced the spider gear in the transmission before I bought it.  It has worked well up until now.  The transmission (or rear axle gear) has started "stuttering" going up hill, almost like a tooth is missing in the gearcase.  But worse yet, going downhill, the brakes will not engage.  They make a racket that sounds like when you throw a car in Park while moving.  While I really like the tractor, I would hate to spend the money on a new transmission, as there could be more problems with it.  What do you think?  From the day I got it home, I have had problems with the starter, and I suppose, that needs attention too.  All in all, would it be costlier to fix it, or just trade it in on a new Deere?  I appreciate any advice you could give me!  Thanks!!

Answer
This is a great tractor. If only it had a hydrostatic trans.
Replaced the spider gears? Mechanic must be having an acid flash back.
The problems you are having are common. Your 180 is getting to the point where if you can't work on it yourself you probably can't afford to keep it. But it is worth fixing!
The brake issue is easy. You have been running the same brakepads since 1998. Hello!!! brake pads!!! 20 years old. You can do the math on this one.
What you transmission needs is a new set of shift keys. There are 4 of them part number M82826 list price 12.25 each. The repair at a Deere dealer is about 3 hours of labor. So about 300.00 total for the repair if he does the brakes while he's there. How mechanical are you? Here's a hint if you pull the trans yourself it should only be about 1 hour labor.
It really won't be hard. 1 belt 4 nuts and 2 bolts. Pull the deck off and take a look. It's obvious how it comes out.
Keep in mind to buy a tractor that will last 20+years you will have to spend 3,000.00 at the minimum. The Kawasaki engine in that old 180 is a bullet proof animal. You will have to go to a Deere dealer to get that kind of durability. I recomend the X300.
But hey, if you are 89 years old, buy a MTD. It will last about 4 years. Unfortunatley when it's new it won't be as good as your 180.