Exmark Quest transmission whine

[TheMaineEvent]

I have an Exmark Quest that is about 15 years old, but well taken care of. As of last year, the mower develops a whine from the left drive wheel after 20 minutes or so of mowing. Once the whine starts I have about 4-5 minutes before the left wheel will not drive the mower forward at all. I have to shut the mower off for 5-10 minutes before I can drive forward, but it quickly gets to an undrivable state again within a few minutes so I can really only get it back to the shed and let it “rest”.
I’ve had the dealership look at it, but they couldn’t see anything wrong. Said the fluid was fine and that the couldn’t recreate the problem which means they didn’t drive it for 20 minutes, but I get it, they’re busy.
I hate to give up on it so I’m looking for help. This model doesn't have a reservoir tank for transmission fluid and I don’t see where to add any fluid, but first and foremost, what could be causing the left wheel to lose power after 20 minutes and develop a loud whine?

 

[bertsmobile1]

The hydro is overheating or perhaps at 15 is plain worn out.
Clean the outer case and check that the fan is actually working & not ripped out of the mounts
If all is good then go to a heavier oil, 40w60 in place of the 20w50 or even Harley Oil 50w75 / 60w80.
The heavy oil will take 5 minutes or so to warm up and drive properly and this is not a fix, just a mehod to squeese a few more seasons out of a failing drive .
Alternately buy the repair kit
The lefts go first beause they are on the slack side of the belt so it slips and the left spins slower.
On top of that the dust from the deck seems to coat the left rather than the right so they end up running hotter .

 

[TheMaineEvent]

The hydro is overheating or perhaps at 15 is plain worn out.
Clean the outer case and check that the fan is actually working & not ripped out of the mounts
If all is good then go to a heavier oil, 40w60 in place of the 20w50 or even Harley Oil 50w75 / 60w80.
The heavy oil will take 5 minutes or so to warm up and drive properly and this is not a fix, just a mehod to squeese a few more seasons out of a failing drive .
Alternately buy the repair kit
The lefts go first beause they are on the slack side of the belt so it slips and the left spins slower.
On top of that the dust from the deck seems to coat the left rather than the right so they end up running hotter .

Thanks for the reply! What repair kit do you refer to?

 

[bertsmobile1]

The valve plate wears groves in it which allows too much oil to bypass the cylinders .
The repair kit ( not cheap ) is a drop in replacement pump & motor unit.
It is a simple enough repair if you are careful and take lots of photos so everything goes back in the same way it came out
The swash plate which controls the speed & direction so go in either way round to account for controls that either pus or pull for forward and it is very easy to fit it backwards for your transmission
And of course the left side has it oppsite to the right side.
The most difficult part is removing all of the silicon used to stick the halves of the cases together without it falling into the case .
Lots of videos showing people haw it is done .
All of them work on the same principle
Big problem is keeping air bourn dust out while the box is open so 3/4 of the video repairs would have failed within a couple of years as they have not practiced proper hygine with the open box
Everything should be covered with a dampened sheet ( not flanalette) or table cloth
Some kits come with new seals but if you don't pull the shafts through the box then there is no need to replace seals

 

[TheMaineEvent]

Thank you for the well-written reply. Very helpful.