93 legacy awd not working?

i have a 93 awd legacy that the awd is either not working properly or just plain sucks, on any type of slippery surface it either wont engage or if it does it disengages shortly after rendering it useless. is that just the way they are or is there something wrong? is there anyway to convert it to full time 4wd like the newer ones are? i can t imagine subaru making such a useless awd on purpose, most fwd cars are better in the winter than mine!

I have an AWD 93 legacy wagon and the AWD is always on if there is slippage from front to rear. Typically the AWD is front wheel drive until the center differential detects slip and automatically shifts some power to the rear until it equalizes.
The unit in the center can go out or lose silicone fluid rendering it useless. The parts are VERY expensive but junk yards sell them for nothing(sometimes). It's easy to test on snow or gravel if the replacement works.

The "new" ones are the same center diffy as the "old" legacy units so conversion isn't needed.

Good luck...