JD 350 Loader

I am doing a service on my 350 and it has a reverser lever on the left side of the instrument cluster opposite the throttle lever. There are two dipsticks on the floor and I assume the front is for the reverser and the rear is for the trans gears. I am wondering what fluids to use in both boxes. I was told that Tractor Hydraulic Transmission fluid will work. The fluid says it meets; JD J20A, J14B, (303) and J14C requirements. I would like to be sure before replacing the fluids. I am also changing all filters. I change the engine filters and oil on a regular basis - but the others I have not attempted. I assume the hydraulic filter is located in the hyd. tank on the right side and gear box filter is located on the right bottom side of the transmission behind a plate with 4 bolts. This year I noticed the trans oil (back dipstick) had turned milky white from water. I intend to let it drain for a few days before putting the filter and fluid back in. Should I flush the box with something like diesel then let it sit to drain?

jd hygaurd or any 303 oil. Rural king has theirs on sale now for 23.99 a 5 gallon pail.

You can use combo trans/hydraulic oil in the trans and reverser as long at it meets Deere HyGuard specs. I would NOT use 303 oil in the reverser. 303 is an old standard and Hyguard specs call for more and different additives. That reverser needs all the help it can get. VERY expensive to fix. The hydraulic tank can use "hydraulic oil" or "hydraulic/trans combo oil." Note that the hydraulic system has two filters, not just one. The filter that comes off with the top cover of the tank is the hydraulic return filter (if it's even still there). Often they are put back on wrong, fall off and land in the bottom of the tank. The reason why they fall of is . . there is supposed to be a long steel dowel inside the filter that allows you to install the long 3/8" bolt good and tight without crushing the filter. That dowel often gets lost. Then the bolt cannot be tightened very much before the filter gets crushed. If your filter is actually still on - you'll see the restriction indicator bounce up and down every time you start the machine. It will stop when the oil gets warm. If you never see it move - there's likely no filter in there at all.
Note: At the bottom of the tank, under the oil is a the steel-mesh hydraulic suction filter. It's often half-plugged because it gets missed. Many owners do not even know it's there. Has spring loaded clips to take out. It's reusable. Just clean it. Often full of old hydraulic cylinder packings.
Besides the reverser oil, and trans oil, you also have to check and add oil to two separate final drive housings via pipe plugs. 90W gear oil is usually used.

Thank you for the help.I did not realize that the hyd system had two filters and I did not realize that my hyd gauge is not there. Doesn't appear to be room for one. I'm still letting the oil drain from the gear box and flushing it some with new oil.

How can the "gauge" not be there? I'm assuming you mean the filter-restriction-indicator. It is built into the top cover of the hydraulic tank. Something has to be there.

OK - I understand - yes that part is there. I misunderstood and was looking for a regular gauge.