Kubota ZD1211 Mower Gearbox oil

[Rob in Ontario]

A few questions. But first tell me if I'm over thinking this. I've searched as best I can and sorry if this has been asked and answered.

I'm going to be changing the Mower deck gearbox oil on my Kubota ZD1211 with RCK60P (side discharge) mower deck. 180 hrs so I'm a little late, manual states change at 150 hrs.

Manual states to use "Gasoline Engine Oil SH or Higher, SAE 10W30"
Dealer says they used 80W90 Gear Oil when I bought the machine.

1. Does it really matter which one to use? Yes it says per the manual to use 10W30 instead of 80W90 but the dealer said they used 80W90 when I bought it.
2. Does mixing brands of oil matter, if I use 80W90?
3. If I really should use 10W30 moving forward, can I drain what is there, and just put in 10W30, or do I need to flush the gearbox out?

Sorry I know I'm probably overthinking this. I appreciate everyone's advice.

Thanks

 

[RjCorazza]

I went through this with my 3 year old zd1211 at the first gear box oil change. 10w30 motor oil in a gear box doesn't sit well with me regardless of what the manufacturer specifies.
I am of the opinion (just opinion) that the 10w30 is for no other reason than to reduce HP load. My Kubota dealer would not comment when I asked about the motor oil in the gear box.
I run 75w140 gear oil in all gear boxes I own, including the zd1211 which has 1300 hours on it.

 

[WM75Guy]

I don't have my ZD1211 manual handy. It looks to me like the manual gives you a choice, .42 quarts of either SAE 10w30 motor oil or SAE 90 gear oil. See what footnote 3 says. Unless it leads you in a further direction, I would put in the one you want.

 

[ROUSTABOUT]

I've over did several of those boxes. I worked at Kubota. There is nothing in that box that will be hurt by either oil. Main thing is keep the level checked.

 

[RBsingl]

One thing to keep in mind is that the number specs in gear lube and motor oil are scaled differently. 30W "motor oil" viscosity is roughly equivalent to a SAE 75 gear oil while SAE 90 would equate to 50W. Of course the additive packages are different.

So the difference between those two lubricant options in the manual isn't as extreme as it might appear.

Rodger