MagnumMZ Trans axle issue

[RDT2]

I have a 4 yr old MZ Magnum with 150 hours on it, and the left trans axle seems to be going out. No issues when I first start cutting, but after 15 min or so, the problem surfaces. There is excessive "whining" from that side, and it doesn't have the power it should have on the left side. If I'm cutting across a hill with the left side on the downhill, it has difficulty pulling itself, and I have to back off the right throttle quite a bit to keep going straight (don't have this issue when the right side is on the downhill). I have a slight incline next to the road that turns to the right as it goes up, and the mower will barely make it up the hill. Bad Boy said it sounds like the transaxle is going bad - really, with only 150 hours?
A new transaxle is $600+, and I'm not sure I want to put that much money (and labor) in a $3400 mower, not knowing if the other side is going to go out as well. Any thoughts?

Forgot to mention - when the transaxle is having problems moving the mower, the left wheel will move in a "jerky" fashion rather than smoothly turn, like the other side does.

 

[Rivets]

The first thing I would check is belt and idler pulley condition. When was the last time you changed the belt and idler pulley and tensioner arm are in good condition and moving freely.

 

[RDT2]

Rivets, thanks for your quick reply on this! I have not checked the belt or pulleys - would this not affect both sides if there was an issue? I will check tonight.

 

[Rivets]

If the belt is worn or tensioner is not applying enough pressure the belt may be slipping on one hydro.

 

[bertsmobile1]

The engine pulls the belt directly off the right hydro so no matter what the right hydro will always spin at engine speed.
The left hydro gets pulled by the right hydro which is taking energy from the system
Because both the left & right pulleys are resisting rotating the belt tensionwill e highest between the engine & right pulley and be lower between the left & right pulleys and be the lowest between the engine & left pulley as the engine is pushing the belt but the pulley is resisting that push.
This is why the tensioner is on that run of the belt
However the tension is not enough and the belt tends to slip a lot on the left side to the point that the left side is nearly always turning slower then the right.
Running slower puts more strain on the pump so the left pumps fail before the right.

To counter this better quality residential & most commercials now route the belt so there is more contact between the left pulley & the belt.
The Z masters have near 180 deg of contact on the left and 90 deg on the right .

Now to add to that, the left side tends to get more dust & debris on it so not only is the oil under more load but is hotter to boot .
It has taken the factories a while to nut this one out as it only rears it's ugly head after prolonged use so does not tend to show up in lab evaluations .