Farmer frustrated with old BCS 725. Issue is functional pto drive, but without power to both wheels at all.Any help is greatly appreciated

[Tjgob22]

As indicated,my old BCS 725 workhorse has seen better days.The issues have stacked up over the years,yet the pto and wheels have always functioned.Ive kept it in one gear at all times-first gear,low-for years.Also,there is a slow leak in one of the wheel seals.But the biggest issue is that there is no power to the wheels in any gear.The pto drives my tiller but the tractor will not drive.i can force the wheels to spin manually by pushing the tractor forward or pulling it backwards.Anyways,this all started after pulling it out of winter storage.I pulled the gearbox cover and inspected the gear shift lever,finding the lever action just fine and spring pins seemingly in the right place.
Thanks ahead of time for and advice or input.