Eaton Fuller 10SP grind when downshfting

Hello,
I have a freightliner FL112 with a 10SP Eaton Fuller, when I am downshifting from 6th to 5th, I flip the switch it grinds very badly. Basically I have to stop the truck, flip the switch for it to drop gears.
Any advise or input?
Thank you.

 

Sounds like a synchronizer issue.

I'd start by checking the air pressure to the range cylinder. There's a regulator on the transmission that drops it down lower than air system pressure. Can't remember the exact PSI spec.

There should be an air filter in there too that can get gummed up and make it lazy. There's also an exhaust port that can get plugged up and prevent air from dumping out of the range piston as well.

 

Is the air pressure range cylinder and the filter all mounted on the transmission itself? Where at?
Indeed, when I am idling I flit the switch up goes fine, down it is a little lazy for sure.

 

Should be somewhere on the transmission. Not 100% sure exactly as to where they'd be on a 10 speed.

 

I think this is the filter you speak of. See picture below with red arrow.

 

it should be hanging on back box, it unscrews and you can get water plus what/ever is caught in filter when you blow it out, its just a filter in the filter canister that un screws?

 

Low air pressure usually makes slow shifts. If it actually grinds you need a syncro