Changing the Hydrostatic tranny fluid. YT 3600

[cr250]

I'm sure someone had this job done right, but  I couldn't find it. So here is how I did it. Looking from the back of the mower, you will see a 6mm allen bolt facing down on the pump, it will be just fwd. of the axel remove this, a spring and a steel ball will come out as well. Drain it, rock the mower to get all the juice out. Install and refill, I used 5w-30, some say to use other, I don't think it really maters. Yes the pump fluid and the differential fluid are separate, use a 80-90 ish gear lube in that. Hope this helps, I'll try posting pics as well.

[rattosh51]

Good tips and great pics cr250!!
Always helps to see the real thing.
Thanks

[big_al]

hey
i had the problem that i lost one ball i first thought it was again correctly but no movement wehen the engine turns   so i doublechecked it and only the spring came out.


Do you think there was a chance that the ball went in n wrong  hole in the valve body ? OR i lost it on the ground

Do you know the diameter of that ball ? that i can get any replacement ?

thaks a lot

[casscounty]

     I don't know why the 3600 would be different, but the service manual for my 6800 calls for 10W-30 for the engine, hydro pump, and differential.

[cr250]

When I posted this I didn't have a manual, that being said, when I pulled the plug for the rear end it sure looked like an 80-90 gear lube, it wasn't dirty so I didn't change it. Most people don't change there car diff lube, these are much slower, I'm not. I believe 5-30 will be just fine, but do what the manual says. I use mine in the winter as well, plus the new oils are much better than they where 30 years ago. Bottom line, use what it says in the manual. Thanks for the correct info!

[YamahaGenuineParts.com]

The drive oil in all the Yamaha Tractors is just 10w30 and is not require to be changed.
Oil is simply pumped forward and backward in the hydrostatic drive system and does not get burnt.
Changing the oil will require the system to be bled as it the tractor will groan loudly until all the air is worked out of the system, this takes quite some time.
Hope this helps clarify things.

Speedy
www.YamahaGenuineParts.com

[cr250]

I respectfully disagree. Everyone I have changed is very dark, after nearly 30 years of operation. Also they must get very hot, why the fan? Just my opinion and observation.

[rattosh51]

Agree cr250!
The sealed "no service" transmission story is just that-a story.
The fan provides cooling and tries to keep dirt and debris off of the hydro unit.
Best thing you can do is make sure the fan is working and the hydro is free of the grass/dirt blanket that keeps heat in.

[dwthompson89]

Did you ever figure this out?  Same issue with mine.

[Bcar7]

Hey! I know it’s been 8 years but did you manage to pull the ball out ? Or added a new one ? I’m having the same issue. Can’t believe it’s made so this can happen 🤯

Edit!!

Found the ball. See pictures, I had to remove the lower side plug and insert a magnet like 8 inches deep to grab it. Maybe I was lucky, don’t know how it’s made inside !

For those who would want to change the oil, I suggest when putting back the bottom plug/spring/ball, to remove the top plug (comes with a spring and a plunger that you’ll have to remove with a magnet) and then install the ball from the bottom pulling it with a magnet from the top. (You’ll understand when you get there..) then install the spring and bottom plug holding the ball with the magnet. Then reinstall the top plug.

By the way you’ll have to remove the top bracket to access the top plug. Take pictures or measurements of the adjustments before.

[rattosh51]

Nice Job!!