Not unless it is badly out of adjustment. Mine was not badly out of adjustment so I did not gain 25% but did gain a little at a sacrifice of reverse speed. Before the adjustment the lever on the hydro pegged on reverse but not on forward. After the adjustment the lever on the hydro pegged on forward but not on reverse. Seems like Husqvarna engineers did not compensate for a loss of lever travel range due to cable stretch as I could not get it to peg in both directions. I would need to modify the linkage to get it to do so but that would void the warranty.
On my Craftsman, the factory design of the linkage did not allow the lever on the hydro to move as far as it could so a modification made it go considerably faster without any change in ability to climb a slope.
Does your tach peg on WOT? My throttle cable also needed adjusting as it was not pegging the governor linkage. I don't trust the built-in tach to be accurate and need to buy a small engine tach. Mine broke decades ago and I've been tuning by ear ever since.
There is only one way to increase the speed of a tractor with a hydro transmission beyond changing the gear ratio (which includes tire size) ... increase the rate of fluid flow. That means either the input speed increases, or the pump displacement increases.
Either will lead to
cavitation which can destroy a pump in seconds.
Yes, it is possible to rob Peter to pay Paul and gain a bit more forward speed, but there is a mechanical limit on just how far a swash plate can be tilted to increase displacement, and that limit is going to fall well short of a 25% increase in speed from the specced 5.5 mph to 6.875 mph at rated engine rpm.
LTs, including the R322, have a rated top speed of
about 5.5 mph. GTs have a rated top speed of 7-10 mph, depending on make and model. If you want more road speed, get a GT with a hydro that can handle the extra load at the rated input rpm without self destructing.