Case 770 PS boy this is gonna be a long one.

[Case Nutty 1660]

This Case 770 diesel powershift that I’m dealing with has some history. It’s an early desert sunset model but it was added to the farm in roughly 79’ I think. Somewhere in 95’ the transmission stopped working properly while my grandpa was mowing. He can’t really remember what exactly was wrong with it but had it sent out to the case international dealership (Bull International was an IH dealer before the merger) and they rebuilt the power shift and replaced the valve body because the c3 valve was sticking with a junkyard one that apparently was good when they tested it. They said the tractor worked great after they were done so we brought it home and it worked for a solid week or two and had the same issue. It was sent back and once again my grandpa can’t really remember what they did to it this time but he remembers a young guy there telling him that one of the spool valve bores felt like it had a little crack in it or something like that so maybe oil was bypassing or something. Anyways we get it home again and my dad takes it down the road for a test and it doesn’t even make it up and down the road before the same problems start up again. They let it sit for a while and soon after the dealership closed down (they had 10k into this tractor at this point) 20 years later here we are and this hunk of iron still ain’t working. Figured I’d fire it up today and drive it around and here’s what we got. Btw I have a fairly good idea of how these transmission work I just haven’t worked on them much at all. So:
Power Shift 1:
tractor seems to bog a little but it works ok

Power Shift 2:
no change in speed but the tractor stops laboring. If you ask me this seems like the actual first power shift.

Power Shift 3:
speeds up with seemingly no bog. If you ask me this seems like power shift 2.

Reverse:
Tractor will stall out and will not go backwards upon releasing the clutch.

So, I’m not sure what these rps trannys have for adjustment or if they have any at all. My only worry is that since the dealership that worked on this tractor was an Ih dealer that maybe they put something together wrong. Just wondering what anyone on here thinks because I don’t know much when it comes to these transmissions or case tractors in general. And don’t tell me to sell it and find another one because my grandpa had some crazy sentimental attachment to his 770 and will not let it go lol. My first thought was was to buy a rebuilt valve body from Elmer’s repair or something to start with a blank slate in that category.

someone has either threw away the relief cartridge's in the filters,, or you never serviced it and it has trash in the system causing pilot spools to stick putting it in two gears at once you need to find some one who knows CASE and not a old ih dealer,, they run thousands of hours trouble free if Correct service is done on them if not you can do thousands of dollars damage to them in minutes,, there is getting less of us around who know how to do the job Correctly these days,, 98% of failures are from improper service practices, no need to replace a RPS shift valve unless its damaged by the repair person,, also they need to be set to shift again by someone who knows how,, takes a few min if you know how,, again you are describing pilot spool stuck probly more than one keep trying to run it and you will take out high dollar parts if you haven't already,,