Fuller 9513 air/splitter problem???

I have an 87 ford 8000 with a fuller 9513 and I can’t split in high range. Low and direct drive are the same speed. One I get into overdrive there is no splitting. Allegedly there is a new slave cylinder per the guy I bought it from. Are the air lines ran incorrectly? Or is this a bigger issue? Thank you!

 

Grinding like things are trying to move but just won’t. I have to put it in neutral, select O.D. And wait till I can feel it stop grinding, then select my gear and keep going. As of right now I basically have to drive it like a 9 speed,

When I have the truck shut off and move between direct and O.D. I can hear what sound a like it going in and out of high and low range since it is quite a bit louder then just splitting in my experience.

 

How would you suggest checking that?

 

I took that air line off and I have air when it’s in direct and O.D. Is that correct?

 

I bought the whole truck it has been like that since I bought it.