If it has Type F fluid in it, use Type F only to add to it. Any Type F fluid will do.
It is recommended to not mix LV(Low Viscosity) Hy-Gard oil with Type F.

 

#29

From the link:

#29·Dec 4, 2006

Hi Guy's. Here is a paste of a service bulletin from when JD quit making the hydrostat fluid.

94-11-30-6
DTAC Solution Number:
16 August 1994
Complaint or Symptom:

• John Deere All Weather Hydrostatic Transmission Fluid (ATF) J21A is discontinued. What do we use?
• Can ATF and HY-GARD® transmission oil be mixed?

Situation:
No published information available.
Solution:
1. John Deere recommends using Low-Viscosity HY-GARD transmission and hydraulic oil (J20D).
2. Only mix ATF with HY-GARD if “topping off” transmission filled with ATF. DO NOT add ATF to a
transmission filled with HY-GARD.
Additional Information:

• Color of ATF will begin to change to a darker brown as larger concentrations of HY-GARD are added.
• When draining and refilling, no flushing is required unless needed to purge contaminates.
• J20A Regular Viscosity HY-GARD has been upgraded to J20C.

J20B Low Viscosity HY-GARD has been upgraded to J20D.
- Low-Viscosity HY-GARD is better than Regular Viscosity in preventing cavitation at start-up. At lower
temperatures, Regular Viscosity HY-GARD gets too thick and may cavitate (create a vacuum void in
the oil due to suction and low atmospheric pressure). This will cause noise and internal hydro damage.
Parts:
Low Viscosity HY-GARD OIL (1) TY22035 1 Quart
Low Viscosity HY-GARD OIL (1) TY22000 1 Gallon
Low Viscosity HY-GARD OIL (1) TY6342 5 Gallon
Low Viscosity HY-GARD OIL (1) TY6344 55 Gallon
TRANSMISSION OIL SUBSTITUTE
All 316, 317, 318, 322, 330, 332, 400, 420 and 430 Lawn and Garden Tractors
M10042

Kent

 

Thanks for the info, guys.

Now that I'm topping it off, one more quick question. As I fill it, will the fluid in the sight tube increase as I fill it, or do I need to put some in, then start her up and work the hydraulic lever a few times, and then let it cool down to get an accurate reading?

Thanks!