Son's 1982 JD 410 TLB has worked fine since he bought it last year, and we changed all the fluids and had the dipper cylinder rebuilt. It's history was documented as not being used for much extensive heavy work with only 1650 hours. Used it yesterday, worked fine grubbing out a bunch of small tree stumps, but after stopping it to grease the hoe, I noticed that the boom only picked up 3/4 of the way up and loader/backhoe/steering functions got slower till nothing but the tractor drive worked. I borrowed a bypass from a friend (ex-JD mechanic)for the D stroke valve, but that didn't work. I can see the coupler spinning at the crank end, bur cannot see if the pump shaft is turning unless I remove the radiator to see for sure I'm a retired truck mechanic, but back injury's prevent me from doing some of the work, but not from coaching my son through it! I would be grateful for any help!
If it's a straight 410 you need to start with the transmission suction screen, make sure it's not packed full of debris. Unfortunately it's in the bottom of the transmission so you'll have to catch the oil. The fact that it still drives should mean it's getting oil but the suction strainer is where it all starts. Then there's a bypass valve in the hydraulic filter housing that may be stuck open. If it's a 410B (I don't remember the year of change) then that machine has the charge pump built into the main pump and it could be plugged suction or a stuck bypass valve in the hydraulic filter head also. There have been cases where the splined drive for the pump shaft has worn out and spins on the pump shaft, so it would be something to check.
The unit is a straight 410, and we did not have the books OR the information of the screen until AFTER the fluid change (Dagnabit!) I take it that the hydraulic pump pulls its fluid from the sump through that screen? It DID have some water in BOTH sumps when drained and the thought was to re-change filters after a dozen or so hours, and it was close to that time to do so
This vintage of Deere is unusual, and this style of hydraulic pump does not suck, it requires some supercharge pressure on the inlet to operate properly. The transmission charge pump pushes oil to the hydraulic pump to a point and then the return oil from the hydraulic system goes through the filter and also adds to the inlet flow to the hydraulic pump. There's a low pressure bypass spool in the hydraulic filter head that maintains inlet pressure to the hydraulic pump and allows any excess oil to return to the transmission sump. If that valve sticks open all the oil dumps back to the transmission and the hydraulic pump starves for oil. It's just one possibility. I believe #20 on the return filter picture is the regulator spool. #16 is the suction strainer.