Your main relief valve is the one on the top right of your picture. It would be set about 2123-2275 psi with engine at 1500 rpm and warm fluid.
Your safety relief valve is the one one the bottom left. It's function is to relieve such as when your going down the road with a heavy implement...
Just make sure you get a filter with an equivalent flow rating. many will screw on which is important, but also important not to choke your pump. with inadequate flow.
the strainer and spin on or both for the transmission/hydraulics. This is the filter I used on my old 2002D. I have no way of knowing whether it would fit your 1602D or not. I can only suspect it would. If you could compare the part # for the 1602 and 2002 you could know for sure. Just make...
What condition was the fluid in? Any idea about last fluid/filter change? If not then yes, change both.
I do not have access to a 1602 parts manual but here is what I think. I circled what I believe might be the flange that covers your internal suction screen. That screen would need to be...
Your 1610 does not have a screw on transmission filter. You do have a cleanable strainer, I believe found behind a triangle shaped flange down low on the left hand side of the transmission (setting in seat left) . Your fluid should be rated for transmission/hydraulic use. Such as john deere...
I don't know for sure but since the 1600 and 1900 are in the same parts manual I would doubt the 2000 pto to be the same. You could compare parts numbers between the two manuals to make sure...
That fluid amount is not unusual for wet brakes. If you have a 1602 that is what you have. There is no eternal seal at the brake rod exit point. That boot is the seal.
This is a new one on me. Parts manual doesn't show dust covers for the 1610 that I can see. Here is part number and one place to buy the turnbuckle. YM3810-REAR AXLE & BRAKES
There should not be oil in there. Either differential input shaft seal is leaking or drop box on 4 wheel drive seal leaking. That setup is not made to be lubricated other than possibly putting a little grease on the drive shaft spline.