Turn the bottle over genius and no gulp.

You pulled off the vent cap?  Man, that's a tough act to do.

J20C vs. J20D: J20C is formulated for normal to hot operating temperatures and heavy-duty workloads, whereas J20D is a lower-viscosity option tailored for cold winter startups so unless you live and use you mower where it get down to -30F so use J20C as your transmission will love you for it and it's good down to 0F .

I had used Dot4 break fluid in my last Cub Cadet and it worked?
this time I went searching for videos because I have a Husqvarna this time
but I figured since it was hydraulic LOL

What did you use to actually get that vent plug OUT???

Like your Hat as well as video.

One thing you forgot, if the fan and pull stich use this stuff xslked Kroil, it will free up ANYTHING

Would you get more out of the vent hole by tilting the transmission backwards?

Factory could have made this serviceable for almost no cost.  2 drain plugs on the bottom and a max level fill plug on the side in an accessible spot.  3 tapped holes and 3 screws.  The machining was probably all CNC anyways so just extra program steps and no labor.   As a hobby machinist I would be tempted to install the drain plugs but access for refilling without removal seems problematic. My JD ZTurn has drains and removable filters and refill thru a remote reservoir. Easy.  Just purchased a new JD rider for around the house so K46 service is in my future. Thanks for the video.

Maybe use a bigger screwdriver to get the cap off😆

Turn it upside down and drain

(When I look up oils , this is what I come up with.)  (Why Mobil 1 15W-50 Crushes it)
The hype comes from the fact that most residential mower manufacturers don't factory-fill their machines with high-end, $20-a-quart commercial hydraulic fluid.

From the factory, your Craftsman Z530's Hydro-Gear units shipped with standard, conventional, off-the-shelf 20W-50 motor oil.

Compared to factory-standard conventional oil, Mobil 1 15W-50 Full Synthetic handles extreme heat infinitely better.

The Thermal Breakdown Point: Conventional motor oil begins to oxidize, cook, and lose its viscosity when it sustains temperatures over 200°F to 220°F. Mobil 1 Full Synthetic is chemically engineered in a lab with uniform molecules that don't begin to break down or thin out until they surpass 400°F.

Why Mobil 1 15W-50 is Unique: Mobil 1’s 15W-50 formulation is not a standard passenger car oil. It is actually designed for high-performance racing, turbo-charged vehicles, and flat-tappet engines. Because of this, Mobil 1 deliberately packs this specific viscosity blend with incredibly high levels of zinc and phosphorus (anti-wear additives) and robust anti-foam agents.

The Verdict for Your Mowers
If you were running a commercial lawn care business putting 1,000 hours a year on a $15,000 commercial mower with heavy-duty Hydro-Gear ZT-3400 transmissions, it would make sense to buy a dedicated commercial synthetic hydrostatic fluid.

But for your residential Craftsman Z530 and John Deere S100, switching them from their cheap factory-fill conventional oil over to Mobil 1 15W-50 Full Synthetic is a massive upgrade. What do you think?

Hydrostatic oil some people say handles heat better than 15 W 50W Mobile One. Is that hyper is that true?

You have stumbled onto one of the biggest, most intense debates in the entire small-engine mechanics world. To answer your question directly: It is a mix of both truth and marketing hype, depending on exactly which fluids you are comparing.

When people claim that "hydrostatic oil" handles heat better than Mobil 1 15W-50 motor oil, they aren't necessarily lying, but they are leaving out some massive technical details.

The differences between the two fluids reveal how they handle extreme heat differently:

1. Where the "Hydro Oil is Better" Claim is TRUE
If you are comparing Mobil 1 15W-50 to a dedicated premium commercial hydrostatic fluid (like AMSOIL Synthetic Hydrostatic Fluid, Hydro-Gear’s own Commercial "Drive System Fluid," or Lucas Hydrostatic Fluid), the dedicated hydro oil actually does have a mechanical advantage.

Hydrostatic systems don't have spark plugs or pistons burning fuel, but they experience extreme mechanical "shearing." Inside your zero-turn's transaxle, steel gears mesh together tightly, and hydraulic pumps slide against steel plates under thousands of pounds of pressure.

Dedicated hydrostatic fluids are engineered specifically to combat this:

Anti-Foaming Agents: When hydraulic pumps spin at high speeds, they can whip motor oil into a frothy foam. Foamy oil contains air bubbles. Because air can be compressed but fluid cannot, foaming causes an instant loss of hydrostatic pressure, making your steering sluggish when hot. Dedicated hydro oils are packed with massive amounts of anti-foaming additives.  
YouTube

Shear Stability: The heavy meshing of gears can physically slice apart the molecular chains of a standard motor oil, causing it to "shear down" and get permanently thinner over time. Hydro fluids are built with sturdier molecular chains to resist this thinning.  
YouTube

2. Where the Claim is PURE HYPE (Why Mobil 1 15W-50 Crushes it)
The hype comes from the fact that most residential mower manufacturers don't factory-fill their machines with high-end, $20-a-quart commercial hydraulic fluid.

From the factory, your Craftsman Z530's Hydro-Gear units shipped with standard, conventional, off-the-shelf 20W-50 motor oil.

Compared to factory-standard conventional oil, Mobil 1 15W-50 Full Synthetic handles extreme heat infinitely better.

The Thermal Breakdown Point: Conventional motor oil begins to oxidize, cook, and lose its viscosity when it sustains temperatures over 200°F to 220°F. Mobil 1 Full Synthetic is chemically engineered in a lab with uniform molecules that don't begin to break down or thin out until they surpass 400°F.

Why Mobil 1 15W-50 is Unique: Mobil 1’s 15W-50 formulation is not a standard passenger car oil. It is actually designed for high-performance racing, turbo-charged vehicles, and flat-tappet engines. Because of this, Mobil 1 deliberately packs this specific viscosity blend with incredibly high levels of zinc and phosphorus (anti-wear additives) and robust anti-foam agents.

The Verdict for Your Mowers
If you were running a commercial lawn care business putting 1,000 hours a year on a $15,000 commercial mower with heavy-duty Hydro-Gear ZT-3400 transmissions, it would make sense to buy a dedicated commercial synthetic hydrostatic fluid.

But for your residential Craftsman Z530 and John Deere S100, switching them from their cheap factory-fill conventional oil over to Mobil 1 15W-50 Full Synthetic is a massive upgrade.

Because Mobil 1 is a full synthetic, it will maintain its exact required thickness on hot South Carolina summer afternoons, it will flow instantly on cool mornings to prevent pump whine, and its heavy-duty racing additive package will protect those internal brass blocks perfectly. You are absolutely on the right track using it—it is miles ahead of what came in the machines from the factory. ( This is what I find when I look it up). Have a good day

I came here to see if it’s worth rebuilding or replacing the Tiff Torque Trans Axle on my old 170. Because he used the word “testaroosky” I will subscribe on that word alone. 🔧 🦌 ⚙️

I sucked the transmission fluid out of my vent port and got about 22+ ounces of fluid out.  I did this 4 times (maybe 5) waiting until I had 2 hours of use, and then I replaced the same amount of fluid back into the transmission.  When I used the entire gallon of 20W50 synthetic transmission fluid, I stopped.  So far, it seems to work better.  (I changed the fluid at 570 hours on my Craftsman pro 42 inch tractor with a Tuff Torq 46.)

A FOOL......

As if he knows 5h1t about OIL...  Says he never used it, but he recommeds it....lol !  Hand in front of the camera, also...clod !

For Christ's sake, use a smaller Dia tube !

Tough Torque - DESIGNED to fail at 200 hours .....  CRAP.

Easy to put drain plugs in that's the best