new project: I bought a 7020 powershift

early this spring I ended up buying a 7020 powershift. The good is it runs perfectly and judging by the hitch ware I believe the working tack and think the 4614hrs are original, very clean and straight tractor still has the factory top link!!! I did have to replace a rear tire as it was shot and it is missing the steering cylinder. I bought it from a guy who used it for snow plowing and other upkeep around his property as well as 25 acers of food plot work, He said it became difficult to shift and some times would not go into any of the ranges so he found a 7060 instead and parked the 7020 for about 2 years then I bought it. I changed the powershift filter before we loaded it onto the trailer to haul home, it would drive itself on the trailer but after running 20 mins would not back its self onto the trailer... its like once the oil got warm and thin it didn't have the power to move its self in reverse under a load. The range and shifter levers are really stiff and have gotten better sense I have been soaking them in pb blaster but they still feel harder to shift then they should be and it still take two hands to get it into reverse any ideas where to start? anyone have a good factory manual for sale? the 7000 series is new to me as our second newest tractor is a 190xt   Thanks

I have a 7060 that has a PD, and no longer have F/S or Park.

Is reverse the only gear it lost?       MACK