If I remember correctly I bought the 5105 that I have in 2000. The rockshaft arms stuck in the up position with the brush-hog attached. My son and I managed to get the brush-hog detached with considerable difficulty. The hydraulic fill cap was removed during various efforts to free the arms. Unfortunately in our case, removing the cap and adjusting the descent control made no difference. I did notice that the hydraulic fluid level was a bit low, so I added some more JD hydraulic fluid. That made no difference either.
I went by the dealer and they provided the information about the spool valve in the rockshaft assembly. I arranged to have them come out and pick up the tractor. The repair was done at the dealership and returned two days ago. The rockshaft arms are working properly with a new spool valve and various gaskets. I also had them replace both flex lines to the front axle power steering assembly. One was leaking and I did not trust the remaining hose due to the age of the tractor. The repair bill came to about $3200 with transportation of the tractor. I am glad to have the tractor working properly again! I wasted no time getting to some delayed mowing on the property.
Thanks to everyone here for ideas and suggestions.
Joe