If it sat for ten years, i'd check the filter, they usually whine when the filter is plugged up. Been a long time since I played with a powerglide,but I think there is also a screen between the valve body and the intake for the pump that could be clogged.Is it an early or late glide some had two pumps,front and rear.The clutch discs need to be soaked and the rubber seals could be dried out,could be a lot of things but check the filter first.Otherwise the glide is not a very complicated trans and if you are inclined you could probably go through it yourself and rebuid it(new clutches and rubber seals) it's not hard.
