Splines on which end?
The splines on the pto flywheel should have some grease in them.
Anything put in the impeller end is going to wash out quick enough, it's just the nature of the beast.
It's a machine, add some lube when you can.
Just to make you think. I had a customer bring in an old sp that never had any grease put in the pto splines. Rust built up, things got worn, the shaft spun and ate the splines, the pto removal tool had nothing to grab, we cut off the pto flywheel.........
Give it a shot of grease.