Case 580ck

Hi, this forum has been invaluable in the past so I am hoping for some more help.
As you know I have a case580 ck that has just recently developed a new problem. The tractor pulls strong in both forward and reverse, and has a power shuttle, but is very slow to engage when using the shuttle
This problem seems to be more evident when the unit is completely warmed up and is present in both forward and reverse
The shuttle was rebuilt about 5 years ago.i am leaning towards the shuttle screen but...

Case 580ck