TO20 hydraulic lift mystery

Resurrecting old family heirloom and after getting it started found that it could only lift blade when moving forward. Removed blade and arms move up and down when very little weight on them. Checked fluid and found not a single full mark on dip stick but has about 4 inches of oil. Have ordered gasket set and watched videos but just wonder if anyone has a guess as to why it will lift when moving forward? Not more than about 10 inches but it won't do that if standing still. Also what type oil is ok to use in hydraulic sump? Thanks for any input.
Can anyone tell me the correct full level on dipstick. Measure from top down probably best.

(quoted from post at 14:18:12 05/31/18) Resurrecting old family heirloom and after getting it started found that it could only lift blade when moving forward. Removed blade and arms move up and down when very little weight on them. Checked fluid and found not a single full mark on dip stick but has about 4 inches of oil. Have ordered gasket set and watched videos but just wonder if anyone has a guess as to why it will lift when moving forward? Not more than about 10 inches but it won't do that if standing still. Also what type oil is ok to use in hydraulic sump? Thanks for any input.
Can anyone tell me the correct full level on dipstick. Measure from top down probably best.

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Good to hear another TO20 is being resurrected. If you drop down to the Harry Ferguson forum you'll get lots of advice and help from people with tractors like yours.

Proper rear end oil level: level with the bottom bolt of the inspection plate on either side. So take that bolt out, let any any flow out. If low, fill slowly until it just starts to flow out.

What type oil: you'll get lots of answers. 90 wgt mineral oil many will say, although that can get quite thick in cold weather. Like many others, I use 15w40 in my TO30. That seems to flow OK at winter temps and still works fine in the summer. And, as one person said, same stuff in the front and the back makes it easy.

As far as the limited lifting: I'm not sure I understand the details. When there is no implement on will the lift operate as normal? If so, then you probably have some leakage somewhere. The best way to start is to pull off the inspection cover, try to raise an implement, and watch what happens inside. Depending where you see the oil shooting out (or swirling if below the oil level) will help direct you. NEVER put your hands inside while the engine is running. Just look.

If the lift doesn't work at all unless the tractor is moving, then I would have to ask if it is the motion or having the clutch out that matters. This lift only works when the PTO is turning.

If I misunderstood completely ask again and someone will understand better than I.

Are you sure it's a TO20?

Sounds like TO35 with the ground speed PTO engaged. Look at the left round cover, see if one position is labeled "ground speed". If in that position, shift it to the other.

Whatever it is, the PTO has to be turning for the hydraulic pump to work.

The oil level should be up to the bottom of the round inspection cover holes on each side under the seat. The dip stick should just be touching the oil, maybe an inch at most. Don't over fill it, you'll get oil in the clutch and brakes.

The original oil was GL1 90 weight mineral oil. That works in warm weather, but using it cold will slow the hydraulics down.
An alternative is 15w40 engine oil. You'll want to drain and refill, maybe flush it. Those are known for water getting in the cases. When you fill it, best to fill it through the inspection cover. If you fill it through the top transmission plug, pour it in very slowly. The oil has to transfer from the transmission to the rear cases. Fill it too fast oil will get in the clutch.

Thanks Jeremy, Good to know about the proper fill level. Once i take the bolt out and find the correct level, i can scribe a mark on the dipstick.

Yes, it does lift when no attachments on the arm or as mentioned when the blade was attached to the tractor it would lift it when moving forward. The PTO spins
when testing lift. I will have a look through the inspection plates.

Appreciate your help.

Tractor was bought new by my Great-Aunt and her husband in about 1951 in Flandreau, SD the year I was born. When I was about 10 my Uncle bought it on their farm
auction. I used to rake hay and haul wagons with it. About 15 years ago my Uncle gave it to me and I brought it up to Minneapolis area where I live. Made a
12volt conversion about 5 years ago and now just getting it back in shape. Plan on a summer painting project this year.

Thanks Steve, It is a TO20 SN36815 I think, maybe 36915, will look when i get home today. It is currently way over full. I will drain it down and try things again, I am sure it needs to be cleaned out good anyway as I know that it has never been opened up. I have a gasket set coming so i will wait until it comes in to drain a bit and check the lift then open inspection plates and see if i can tell where it is leaking past a seal or piston. Also see about the check valve too. But, regardless it needs to be cleaned and checked.

Thanks

I?m pretty sure you have to have the clutch up for the pto to turn, hence the reason it will lift moving forward, or siting still with no implement. It?s not a live pto.